I think it's about someone he cares about but she doesn't feel the same about him, or at least doesn't trust him. No matter how hard he tries, she doesn't let him in, and tell him whats wrong. It just pains him to see her suffering. The harder he tries, the more harder she keeps him away, even though he just wants her to feel better, and it's destroying them both. And it's very difficult for him to let her go, hence "the trouble I'm in".
I think it's about someone he cares about but she doesn't feel the same about him, or at least doesn't trust him. No matter how hard he tries, she doesn't let him in, and tell him whats wrong. It just pains him to see her suffering. The harder he tries, the more harder she keeps him away, even though he just wants her to feel better, and it's destroying them both. And it's very difficult for him to let her go, hence "the trouble I'm in".