I have a friend like this. She was dating a guy and then they broke up. After that one day he raped her. She was traumatized like all victims are. Even after that incident she even hooked up with him for a last time, did the thing where she tried to stay in control this time to regain that sense of power. After this she maintained contact and interaction over the years. Eventually got married and still had contact with this person. This guy was still trying to get with her. It took a long time with me talking to her for her to understand that this person she knows so well and has good feelings for was a monster, she just couldn't see it. She allowed this guy to cause friction in her marriage, almost to the point of divorce. She still wanted friendship and to talk with him. The thing is, because of the history and past relationship the person has a lot of privileges and it's a strange thing how those privileges don't disappear even if this person does something heinous. You will often accept a spouse or partner doing something to you that you will not accept from anyone else e.g. shouting at you. That's because they have a privilege someone else doesn't have. Raping you is not a privilege anyone has, even this guy you've know for so long.

Your continued contact with this guy is going to destroy your relationship and any you may have in the future. This person has a sexual interest in you that even if you don't reciprocate, they get to continue feeling that and thinking about you in that context when you interact. It's infidelity from their side of things but you're facilitating it with allowing contact and it's wrong of you to accept any attention or connection from this person when you know that sexual/romantic interest is at the heart of that contact.

You need to get clear on what you're doing and stop setting up this new guy you're with for some serious hurt and disappointment. Either tell people what happened so you can get support to deal with this or at the very least cut all contact. When considering this you will get a true sense of how you feel about cutting the attention you get from this guy and if you're being unfaithful to your bf in the privileges you give to him.