Back together but maybe seperating again?

[Jealousy]

I have suggested many things, movies, mini putt, go karts, things we both enjoy (tho he claims we have no common interests). I've even suggested fishing (ugh). When he goes out with his friends he makes up reasons about why I shouldn't go, makes me feel like he's embarrassed by me.

Unfortunately things have taken a quick turn within the past week and a half. When he had moved out the first time, a female friend (friend only) and him rented a house together and things went sour when she was always having male friends stay over, never paid her half of the bills and eventually quit paying rent. They haven't spoken for about six months and this is not the first time she has screwed him over. Than suddenly all is forgiven and they started hanging out again. She lives around the corner from us and he has been going over for several hours at a time, coming home even as late as 5:30am (This is normal for him with male friends as well). But he knows this drives me crazy and pulls the jealousy card on me all the time. NOBODY likes this girl, all of his friends hate her and his family can't stand her. I know he's doing it to spite me. Its like he's sabotaging his own marriage.

I know for a fact that he's not cheating, but have wondered if there is some type of emotional affair going on. I have recently realized that he seems to stop being friends with her when she is dating someone and is her bff again when they break up (they literally started hanging out again within days of her and her bf breaking up). When they were living together he was down right ticked off that he could hear her and men having sex, even told her she couldn't have male friends staying over and such. If anyone says anything about her he gets very defensive, he actually verbally attacked me the other day because I refuse to be her friend again because he doesn't understand why I don't like her. I just don't get what he sees in her, she very selfish and arrogant, ships her kid off as much as she can, doesn't work and when she does its for a week or two before she gets fired, shes a dead beat pot head. The first time we split it was because of all the time he was spending with her and here we are again. I don't get it.

Vent over, sorry