Help, How Do I Get Over Lies and Heart Ache

Me and my boyfriend have been dating for three years now. We have had our ups and downs. But getting to the point. Recently we have been having lot sof trust issues, well I have. One day I seen him calling other girls beautiful. Not only that but basically saying the things to them he says to me. It hurt I confronted him and I thought I could move past it. I seen him sneeking trying to talk to old friends and new friends that have "thing" for him. This is not the first time. This has been going on since I made everything official. I don't know whether to trust him or move on. I just really want to see what other people think. Im still young and have a lot of room for growing and improving. Just hopefully someone can help me think better, and that I'm not over reacting.

Thanks!