To me, this song is about a boy that falls in love with a girl and all of her imperfections. She's so insecure though that she does all of these things to change herself and make herself "perfect." The boy thinks that she won't love him anymore after doing this (I don't think you'll ever want to love me.) he doesn't want her to change and he thinks she's already perfect. He says this because after she's made all of these changes to herself she doesn't want to face him and hear everything he has to say about what she did.
And she could make hell
Feel just like home,
So I'm never leaving her
No matter what he's going through or where he is, she makes everything okay. "So I'm never leaving her alone" He'll never leave her because she makes everything better.
home,
Can I even
Complicate your breathing?
I guess I'm just your average
He's asking a girl if he makes her nervous or is excited to be with him. "I guess I'm just your average boy" He realizes that she doesn't like him and thinks of him as an "average boy."
Now the doctors dancing in,
While the ambulances sing.
Another boy without a sharper
"Now the doctors dancing in" The doctor is running into the hospital room to help him. "Another boy without a sharper knife" A boy tried to commit suicide by cutting himself but he didn't cut deep enough and ended up going to the hospital instead.
the best time of my life
But now I sleep alone
(Sleep alone)
So don't
He's saying how being with her was the best time of his life. "But now I sleep alone." He means they lived together and obviously slept in the same bed but now that she's gone he sleeps alone.
it feel
(How does it feel?)
How does it feel well it feels like I'm on fire!
Wake up I know you can hear me!
Make me
When he says 'How does it feel? Well it feels like I'm on fire!" He's talking about how it feels to be without this girl. When he says "Wake up I know you can hear me!" The girl is dead and he's telling her to wake up because he wants to think she's asleep.