Is it normal to become bitter toward someone during a long term relationship?

I know you say you love him and he is still very sweet, but it sounds to me like you aren't really emotionally invested in the relationship anymore. He betrayed your trust and he's going to have to work really hard to get that trust back, if it's at all possible. I think you will have those untrusting thoughts in your head for awhile. The fact that you are really socializing with his circle of people anymore says to me that you are scared of getting hurt like that again so you don't want to get to deep emotionally with him again because you don't want to feel that pain that you felt. You might want to look into couple's counseling so you guys can get your feelings out and work on building that trust back up. If that doesn't work, then I would say that the relationship needs to be over.