is this crazy thinking to think maybe it was just me that made him like that?

Cant get this thought out of my head, its like if i cud just know he isnt treating his new girfriend anybetter id feel more reasured it wasnt me? I was really insecure and needy and quite paranoid about him being friends with other girls which caused a lot of arguements between us, as the majority of his friends were in fact girls.

I no i shud only be concentrating on my own healing but sometimes cant help wondering if it was just me or was is he an N and will never change. He was really harsh on all his previous girlfriends, and dumped them all in the same way and moved on within a short space of time. He also admitted cheating on the majority of his exs, oh yeah and said they were all psychos apart from one who was nice but the feeling wernt there so the evidence is there isnt it, but its just the girlfriend hes with now seems to be getting the best of him, he would never do half the stuff he is doing with her with me, and he is also being a 'good dad' in the last few months which makes me think he is happy with her coz he was a rubbish dad when we were together and i did everything.

Maybe its just the obsessive thoughts again? I dont no. How do i snap out of it? Its like if i new he was just being the same with her id be able not be as botherd does that make sense?