Why do guys do this?

Ok so I hooked up with a friend of mine a few months ago he is someone I never though I would like in that way ever he use to annoy me and everything elese at first untill I hooked up with him then I all the sudden got feelings for him and he is just about all I can think about. I told him how I feel and he was very honest with me in the fact that he never sees us being anything more then friends ever so I know he does not like me or anything like that thats not my question lol. But when we talked about not messing around anymore because of feelings he told me maybe some where down the road we can do it again lets just leave that one open, that was 3 months ago and we have not done a thing since. Well he is always asking me who im sleeping with now and gets jeaslous of the guys Iam dating at the moment. I just lost over 100lbs last year and when him and messed around I was still bigger now that Iam skinny he acts this way could it be that no im skinny and looking good he may want me?