Note: The phone conversation we hear is not really part of the song, but an addition for the video. According to the conversation he left her, according to the song she left him. And this is not the only confusing thing about this song.

GONNA= (coll.) Going to.

I GUESS= (coll.) I suppose.

DÉjÀ VU= /deɪʒæ vu:/ (originally a French expression. It literally means “already seen”) If you see a place for the first time and have a déjà vu, you have the strong sensation that you have seen that (or lived that experience) before, even if that is impossible. For example, you go into a house you’ve never been before and suddenly you feel like you already know the living-room, or you need to go to the toilet and you know exactly where it is. Some people think this is a paranormal experience, some people think it’s just a trick of the mind.
Actually, in this song the term “déjà vu” is not used properly because if you walk along the street and see a person who is very similar to some other person you know, that’s not a déjà vu, that’s simply that they look similar.

THIS CAN’T BE TRUE= This is impossible.

CAUSE= (coll.) Because.

MOVED TO= If you move to another city, you leave your house and go there to live.

OR WHEREVER= Or any other place I can’t remember.
We add -ever to all interrogative words to form a compound meaning “it doesn’t matter wh...”
- I’ll go with you wherever you go= I don’t mind where you go, I’ll go with you. If you go to Madrid, I’ll go with you, if you go to Mexico, I’ll go with you, if you go to China, I’ll go with you.
- Whoever you are, stop right there= I don’t know who you are but stop.
- Whatever you need, just tell me= It doesn’t matter what you need, tell me and I’ll try to help you.
- However you try, you won’t be able to open it= You can try to open it in every possible way you can think of, but you will never open it.
- Whenever I phone her, she’s always busy= Every time I phone her she’s busy, always, it doesn’t matter if I call her in the morning, at night or at lunch time, she’s always busy.

GET AWAY= Escape; leave.

THAT ONE NIGHT= That night.
We add ONE to THIS or THAT to emphasize that we are talking about something unique and special, not just one more thing.

MORE THAN JUST RIGHT= If something is “just right” it is good, not too much and not too little. If something is more than just right it is really good, perfect.

I WAS ALL THROUGH= If you are through, you feel devastated, destroyed, and life makes no sense to you. Also, if you are through you have finished with something, so this expression may also mean that I have finished my old ways and am ready to start a new life.

OVERWHELMED= If you are overwhelmed you feel that the situation or the emotion is too big or strong for you to handle and you feel paralyzed.

FRANKLY= Honestly, to tell you the truth.

SCARED AS HELL= /skeə*d/ If you are scared, you feel very afraid. We use the expression AS HELL after an adjective to make it stronger (and it can be a little bit rude, as many colloquial emphasizers, so don’t use it in formal situations).
- This car is fast as hell.
- Timmy has grown a lot, he's tall as hell.

FELL FOR YOU= If you fall for somebody you fall in love with them, usually in a quick and strong way, and often superficially though intense.

YA= /jə/ You.
This pronunciation (sometimes spelled like “ya” in colloquial writing) is a weak form of YOU and it is quite common in conversational speech. It is often opened (as final schwas /ə/ can be) and sounds more or less like /jʌ/, but not in this song.

DRIVE BY= A drive-by is when you drive your car past a place but you don’t even stop there. Here he is talking about their one-night love and says that it was not just a one-night thing, like a drive-by, but he wants it to be a more permanent thing (he wants to stop his car by her side, not keep on driving alone). So the sentence "This is not a drive by" means "I'm here to stay".

A TWO-PLY HEFTY BAG= If a thing is HEFTY it is strong and/or heavy, powerful. TWO-PLY means that it has two layers (as in "two-ply toilet paper"), or if it's thread, two thicknesses or strands. If the bag is heavy it needs two layers to make it stronger, or it may break. And why does the singer say that he needs a two-ply hefty bag? Because the love he feels for her is so big that he needs a very strong bag to contain it:
(This is) just a shy guy looking for a two-ply hefty bag to hold my love.

TO HOLD= To contain.

MOVE= If somebody or something moves you, you feel a strong emotion.

GROOVY= (a bit old-fashioned) Cool, fantastic, fashionable.

SUE ME= If you sue someone, you start a legal process against somebody because you think they did something bad to you and you want justice or compensation.
SUE could also mean to court or woo someone (trying to seduce her), and that meaning fits here much better but it is very old-fashioned and I don’t think anybody would think about it in this context. In conclusion, the sentence “They don’t like it, sue me the way you do me” makes no sense to me :(
When he says “They don’t like it, sue me”, maybe he means “they don’t like it, so they can sue me (I don't care)”, but still that makes no sense, who are they and what is it that they don’t like and why? Confusing.

THE WAY YOU DO ME= Like you do to me, in the same manner.
The verb DO can be used as a pro-verb when we can’t or don’t want to repeat a normal verb, so in this sentence DO means SUE (Sue me the way you do me).

DOWNWARD SPIRAL= The adjective DOWNWARD means “going down, moving down”.  A spiral is something like this. A downward spiral here means “a vicious circle”, because you move down and down and can't escape. As an emotional metaphor, down is bad and up is good, so when you feel LOW you are sad, depressed, and when you feel HIGH you are happy, euphoric (naturally or because you are on drugs). So if your life is moving in a downward spiral, things are going more and more pathetic.

WENT VIRAL= If something goes viral it becomes very very popular (especially on the Internet). So the sentence “my love for you went viral” makes no sense because if a love goes viral it means that everybody falls in love with her (she becomes very popular) but he says “my love”, so if it is YOURS it can’t go viral because it only belongs to you. But really, what he means by that is that he became obsessed with her and loved her more and more. The expression is no correctly used but the meaning is obvious anyway.

I LOVED YOU EVERY MILE YOU DROVE AWAY= Again he’s using cars as a metaphor to explain what’s happening.  We now know that he spent a night with her and then she went away, but now she’s back and he’s trying to convince her that he loves her and wants to spend his life with her. What he says here is that even when they were separating, he loved her, and as time was passing by (distance was getting bigger), his love was growing stronger.

SKIP= If the normal procedure is to do A, then B and then C , when you skip B, you go from A to C but don’t do B as expected.

HOW-YOU'VE-BEEN= (coll.) In theory it means: How are you? How have you been? but in practice it is normally used the same as How's it going?, which is not really a question but just a way to say Hello. He doesn't say how-have-you-been? because he's not asking a question but simply mentioning the expression. No question, no inversion.
SO LET’S SKIP THE “HOW YOU BEEN”= I don’t want to start with social formalities, like trying to be polite and have small talk to know each other before we can get more intimate. We’ve already been together, I love you very much, so let’s start a love relationship right now.

GET DOWN TO= If you get down to something, you stop waiting or preparing and start doing something.
- Stop talking and get down to work, it’s late!

MORE THAN FRIENDS= Lovers.

HIGHLIGHT= The most exciting or memorable part of an event or period of time.
- For me, the highlight of my trip to Spain was the day we spent in Toledo.

UNTIL I CAME TO= To come to means to recover consciousness, so frankly, I don’t understand this sentence very much. Maybe he means that the night with her was so ecstatic that he lost consciousness and when he recovered consciousness he knew he needed her because he was in love, or maybe he had drunk too much or something and he passed away.

THERE’S NOTHING UP MY SLEEVE= This language comes from magician shows. If a magician is playing a trick with cards he may put a card up his sleeve to hide it, and then take it out at the right moment to fool people and make them believe that he made it appear magically. So if we say that we have nothing “up my sleeve” we mean that we are sincere and don’t want to deceive anyone, we mean that “what you see is what you get”, we are not lying or hiding anything.
THERE’S NOTHING UP MY SLEEVE BUT LOVE FOR YOU= My love is real, I only have love for you.

TO GET MY HEAD TOGETHER= (coll.) If you get your head together you make a decision or you put your ideas in order.