I see this song as being about him losing his father and then feeling like because of his mourning he's grown distant from his girlfriend and doesn't think that she understands what's happening to him and she wants to leave because he's not really there anymore. But, he's saying, "You don't get it. I've lost so much." And then there's the verse about, "I want to live like we did before all this hit: to sleep in your arms, to think we'll never fall apart." Basically, the death of his father also triggered the deterioration of his relationship with this girl.
I see this song as being about him losing his father and then feeling like because of his mourning he's grown distant from his girlfriend and doesn't think that she understands what's happening to him and she wants to leave because he's not really there anymore. But, he's saying, "You don't get it. I've lost so much." And then there's the verse about, "I want to live like we did before all this hit: to sleep in your arms, to think we'll never fall apart." Basically, the death of his father also triggered the deterioration of his relationship with this girl.