DAMN= An interjection used to express anger, irritation, contempt, or disappointment.

THE DOCTOR'S JUST FINISHED TELLING ME= The doctor has just finished (we use JUST with the present perfect to expressed an action that finished at this very moment or a very little time ago). Finished telling me (the verb "finish" is followed by -ing). So this sentence means: "the doctor has told me a moment ago that there's no time."

LOSING YOU COULD BE THE END OF ME= The subject of this sentence is "losing you". In English we usually use the -ing form when a verb is the subject.

I SHOULD DO THE THINGS THAT I WANNA DO= The doctor told me that I'm going to die (there's no time) so he said that I should do the things that I want to do because I will die very soon and I will have no time to do them later.

WANNA= Want to (conversational English)

WITHOUT YOU= The "perfect" pronunciation of this is /wɪðaʊt ju:/ but because the sounds of the T and Y come together we usually make an assimilation (T+Y= CH) and pronounce it /wɪðaʊtʃu:/

HOW COULD I WITHOUT YOU?= how could I (do the things I want to do) if you're not with me? = I can't do it without you.

COS= Because (conversational English). Also spelled: ‘cause, ‘cos, coz, cuz.

YOU'RE THE ONLY ONE I LET IN= You are the only person I allow to come into my heart.

HOW TO STOP THIS FEELING SPREADING= If something spreads, it extends through a bigger area. If a feeling spreads, it becomes more intense. The verb STOP may be followed by -ing or by infinitive with TO, but with a change of meaning:
- When she arrived, I stopped smoking = I was smoking, and when she arrived I stopped; I put my cigarette out.
- When she arrived, I stopped to smoke = I was doing something and when she arrived I stopped doing that because I wanted to smoke a cigarette (purpose infinitive).

I'M HOPING= We use the continuous form to talk about something which is happening at this moment. But the verb HOPE is one of the verbs that don't use the continuous form: verbs expressing mental and emotional states don't use the continuous form.
- I don't understand this (not: *I'm not understanding this)
- I love you (not: *I'm loving you)
- I hope she gets well soon (not: *I'm hoping she gets well soon)
But all these verbs may use the -ing form in some special cases, often with a special meaning:
- I'm tired of understanding (all verbs use the -ing form if they go after a preposition or conjunction).
- Understanding is the first step to love (all verbs use the -ing form if they are the subject of a sentence)
- I'm loving it (Mc Donald's slogan): emphasis
- I'm hoping that you know: emphasis

SOMEHOW= In some unspecified way.

LET'S JUST GET BACK TOGETHER= In this sentence JUST is emphasizing = simply.

WE SHOULD'VE NEVER BROKE UP= We should have never broken up. This irregular verb is BREAK-BROKE-BROKEN, so it should be: "we should have never broken up". But in non-standard English it is BREAK-BROKE-BROKE, so in colloquial English we can use BROKE as the past participle of BREAK. The phrasal verb BREAK UP means to stop a love relationship, so if you break up with your girlfriend you leave her and you're not boyfriend and girlfriend anymore.

HEART= pronounced /hɑ:*t/

BEAT= If a heart beats, it is pumping blood all around your body. If a heart stops beating, you die.

FUNERAL= The religious service held for a dead person before they are buried or cremated.

IF I DIED, WOULD YOU COME TO MY FUNERAL?= This question (would you come...?) is not an invitation, it is part of a conditional sentence type 2. These sentences express something which is possible but not probable, and we use the past tense in the if-clause and WOULD in the main clause:
- If you died I would go to your funeral.

WOULD YOU= The "perfect" pronunciation of this is /wʊd ju:/ but because the sounds of the D and Y come together we usually make an assimilation (D+Y= J) and pronounce it /wʊdʒu:/ .

WOULD YOU CRY= The first part of this sentence is understood because it was said before: if I died, would you cry? The same thing happens with the next sentence: if I died, would you feel some regret that we didn't try?

FALL APART= break down, collapse emotionally, have a nervous breakdown.

THE SAME AS I= In comparisons, if we use a pronoun we have three options:
1- He's bigger than I am (if we use the verb we need the subject pronoun)
2- He's bigger than me (if we don't use the verb we use the object pronoun)
3- He's bigger than I (if we don't use the verb we can use the subject pronoun. This form was considered the only correct form, but now it is considered very formal and rarely used in conversation). They use it in this song because it fits the rhyme.

HAUNT= /hɔ:nt/ If a ghost (spirit) haunts a house, it is always inside the house and you can see it or feel it sometimes (we call it "a haunted house"). If a ghost haunts you, it visits you frequently. If an idea haunts you, it's always on your mind, it obsesses you and you can't stop thinking about it.

YOU MISSED YOUR CHANCE= If you missed a chance, you had the possibility to do something but you didn't do it at the right moment and now it's too late.

CPR= Abbreviation for cardiopulmonary resuscitation (latin words: cardio= heart / pulmonary= related to the lungs / resuscitation= the act of bringing back to life). When a person dies you may try to resuscitate them for some time by pressing on their heart rhythmically and breathing into their mouth.

MEND= Fix, repair, restore. In this song it means "heal" (restore health).

IF I GO, I GO= If I die, then I will be dead (if you let me die, there will be no second chance to help me). Another possible meaning (more literal) is: if I finally decide to forget about you, you won't be able to have me back, so hurry up or I'll stop waiting for you.

BEGGIN' = Begging

DON'T LET ME GO= Stay with me.
The verb LET can mean ALLOW, but the expression LET ME GO means "stop holding me, I want to go away". So "don't let me go" means "I don't want to go away from you so stay with me".