Can you please help, relationship problem and trust problem?

Does my boyfriend have the right to touch whoever he wants. For example he is friends with a girl called Rebecca who I am not ok with because I have a problem with her because she takes drugs. I don't know why I have a problem with it I just do. I know she is allowed to do what she wants, I just didn't like the fact that she would smoke the stuff when my boyfriend was at her house and she has driven him with cannabis still in her body. I also have a problem with her because whenever Rebecca and David would meet each other at the beginning of our relationship she would greet him by grabbing his backside, which I am not ok with. Since we are going out and she is more aware of that, she has stopped that. But I still find it annoying, She also has a picture on facebook that looks like a couples picture for her profile picture which kind of annoys me. For some reason I find it difficult with them being friends ( I would NEVER EVER tell them they can't be friends as that is not my choice, his choice completely, I am not a psyco girlfriend that stops him seeing people). I am a little threatened by her, I know I need to trust him, but I find it hard. When I say he touches her I mean like shaking hands, taping her on the shoulder, touching her back if he is trying to move her. I know I need to be less rigid about this stuff but I don't know how. He said that he will not stop making physical contact with her. I got angry about this, so angry that I stabbed myself in the arm with a fork. (That was psyco I know, I will never do that again, I got really frustrated and had lots bottled up over other stuff and needed to release my anger some way and I chose to do that). I really need help.