Should I leave him?

Well, I have a boyfriend and he is wonderful, but there is one thing that really,really bothers me.

He has a "best friend" who is a girl and also his ex. Problem is he talks to her every day, confines in her, tells her our problems,my problems and lately he mentions her almost every time we talk. She is married tho,with a kid and pregnant again but as she said she just knows she will eventually divorce her husband. I don't know her,or do I want to know her. I'm thinking of leaving my bf because of this as he does not see the problem, because, I quote "they were together long time ago so it doesn't count anymore" 🙄

He says he is having hard time connecting to his male friends and it's easier for him to talk about sensitive and intimate things with a girls., especially his emotions.

He also told me few months ago that he would probably date her if she is divorced and he is single and I'm out of the picture and because they were together he is obviously attracted to her. When they were together he moved into her city and he told me few days ago that he never will forgive her that she didn't told him how far his new neighbor is from hers,because if they lived closer then they maybe never broke up. She dumped him and he still doesn't know why and I think it bothers him still.

I must say he is very lovely, gentle,caring but I feel like I'm in relationships with him and her.

Beside this,we don't have and problems.

He is genuinely very nice and good person but I don't think I can deal whit it.