I'm not going to break up with my girlfriend
Are you sure you don't want to break up with your girlfriend?
No, I love her too much even if she is cruel.
If your girlfriend is mean to you, it is wrong to stay loyal to her when that isn't what you feel. Move on with your life and find someone who will treat you with respect.
Her back was hurting, and I felt sorry for her.
Still, if she is mistreating you then you should leave her. She'll be fine with a doctor, she doesn't need you to take care of her.