I started dating a man last april, we have known each other for 10+ years but never got involved in the past. At the moment it is a long distance relationship as we live in different countries now, but we talk/video chat several times a day and visit each other whenever possible.
He had relationship issues in the past, he was very honest about it and told me all about his past relationships and what kind of dynamic and patterns they involved. He was attracted to cold and distant women. He had a 12 year on/off relationship with a woman. During the course of those 12 years they pretty much tried everything to be together but it always ended in fighting and they never spent more than a week together at a time.

In August he told me he wanted to confront himself to see if the old pattern still attracted him or if he was getting over it as i'm neither cold nor distant. So they ended up in bed together... he tells me it wasn't cheating because he told me beforehand, but I still feel cheated. he also claims there was no penetration, only touching. She suggested they continue having sporadic sex even though she has been in a relationship for almost a year.
He didn't tell me right away, all he said is he wanted to come and visit as soon as possible to talk about it, so my mind went to all sort of places and in the end i confronted him 2 days later saying it couldn't wait for him to get here, I needed to know right away what happened or he should not bother coming. The whole thing made me really insecure and has taken a toll on my self esteem.
I never liked her much before that, but since I have developed a hatred for her, my problem is he still sees her every month or two for work, and every time I get really worked up, jealous, insecure, angry and bitter and I do not cope well with the situation. Also she has no boundaries with him whatsoever. She keeps phoning and texting him in the middle of the night, I know she does this regularly and all he said was she has no sense of time, I hate that he won't set any boundaries... When he talks to her he still refers to her in cute nicknames. He claims their relationship is now neutral but still won't take me with him when they work together, he says we'll "scratch each others eyes out" and that the tensions between us would affect their work.
I want to believe that he is faithful to me, I know he loves me, but i'm really struggling here, does anybody have some advice for me?