so hurt and confused

The other night my bf told me he was getting a friend to drop him off after  work. I was thinking it was one of his coworkers . I come to find out it was the girl we met at a party 3 days ago. She agreed to pick him up from work and to help him study for math. He didn't tell me nothing like that and when I ask what he was doing that night he just replied" doing hw".  He lied to me . I had to ask him who dropped him off to find out it was her ! Supposedly she was over there for a while , from like 11pm -2 am. I don't trust him anymore and thinking of breaking up with him...any experiences/opinions