So I had two friends date each other and eventually get engaged (he was 21 she was 19) They shared an apartment and I often visited them a to hang out/talk. Well about 3 close to 4 months ago they separated(he broke up with her). I have been friend with the guy since high school so for the past few months I have not talked to her but since this time hes probably had 5 or 6 new gf and no telling how many chicks he has picked up at bars. Well about two weeks ago I started to talk to the girl (like a friend nothing more. Kind of like old times) I told them both that I was not going to pick a side/exile one or the other.(I mean damn we are adults now and should have to be immature about things of this nature) Well he keeps blowing this up in his mind(he has a tendency to be immature) I have reassured him several times that there is nothing going on between us but I don't think he wants to believe it. What should I do?