I'm not what s/he says I am because s/he wants some relief,
I did what s/he says I did, but against my choice,
He should be mine but he would be new,
The happiness I had is gone forever...

First line: Pretty straight forward. The subject claims to be something that it is not, for the sake of someone else feeling relief.

Second line: Again, straight forward. The subject claimed to do something, but not at will.

Third line: No idea what this is supposed to mean.

Fourth line: Straight forward once again, the subject used to have happiness, and that happiness is gone.

I'm stumped.