Need advice

I need some advice with my boyfriend. I want to know if I made the right choice or not. A little bit of my boyfriend. He is mid twenties, he has BPD (borderline personality disorder. He takes med for his anxiety and BPD. He even see a psychiatrist twice a month. I have found out that he likes to talk to other guy on Craigslist, I have looked through his phone and I've notice he has been talk to only two guys who are super Dom, and he is sub towards. I've ask him why he talks to them. When he know that he has a great amazing boyfriend who treat him well and give him everything he needs. He doesn't know why he does, but he said that he is going to his therapist to help me solve this matter and to see a solution out of this. I can understand where is he coming from. I've been able to pin point some stuff in his past that make me do this. He said that it's not a fantasy or a desire, he can't actually do it to himself. Or actually do it in person. I've even ask to perform some of things he talks about, but he said he can't cause he doesn't want to be hurt or hurt me. He likes to get off by what he reads or send. Just two weeks ago. I gave him the open door to let him talk to this guys almost like an open relationship to him but not for me. I only did instead of him doing behind my back. I've done a lot of reading on BPD and i understand a lot of his disorder. This past week he has been talk to them alot only when I am not around him. Did I make the right choice or not, or how do I confront this matter or how do I help him with this matter. Please help with any advice or solution. I am desperate for an answer.