Story goes like this and I'll try to be utmost honest about everything. 

 I started dating my gf almost a year ago. We do LDR. I visit her every 1 and a half month. I am in Thailand and she's in UK. We have to be apart because I am a student researcher in an American university in Bangkok and she's currently pursuing her degree there. 

 Before I dated her, she used to date one of my close friend and they were serious. While dating my friend, they fought a lot, broke up many times and my close friend cheated on her woth several women and I knew all of it. My friend also have commitment issues too. She didn't know much about him and his behaviours since they started  doing LDR in their second year and their relationship lasted for 4 years. While they broke up many times and between those different intervals, my gf had a guy that she used to see. Let's call him John. Nothing serious, just for sex. John was also having problems with his gf. 

That shitbag, instead of fixing his problems with his gf, took a "break" from his relationship and had sex with my gf on every interval of her breakup or every occasion imaginable. Loose moral. I don't think a guy should have sex with another woman while they have a relationship on limbo. John was not absolute with his gf either and they were taking some time off. Even while sleeping with my gf, he met up with his gf.

Please note that John also had a couple of relapses with my gf after getting back with his gf after a long time and then my gf started seeing her ex, my close friend again. My close friend somehow had some hints about John but never knew the whole story. 

Most of the time my gf and my close friend fought was because my friend had big suspicions about John who also was, flirtatious, forthcoming and downright told my gf to break up with my close friend because they were toxic. 

Here's the problem. I don't trust that guy. I think that he took advantage of my gf and her vulnerable moments. I also think that it was not right for my gf to have had sex with John while he had an ongoing relationship. Before I dated her, I knew that she had a thing with John, but I found out about most of the intimate stuffs later when she told me incrementally, in episodes.

 
All in the past, am I right? No. John is now back with his gf and apparently told his gf about his past with my gf. But instead of letting the past guide his conscience, he kept inviting my gf out to bars, ball dances and even to an Ireland drinking trip on the dates that I was visiting her. It's annoying because my gf was interested in all of those offers. All of them. 

I don't want to be a self-righteous asshole.

Most of their sex related stories happened after being drunk. I am in a long distance relationship with her and I truly love her. I worry. I told her that if John keeps flirting and inviting her out to those functions, I will have a conversation him. I told her to stay away from John too.

Am I the asshole boyfriend? 