Jealousy problem? please help 10 points for best answer*?

The main thing you need to do is don't bother him with it to much because if they are just friends it's might make him brake up with you if you get on his nerves, and if he is cheating it will adventully come out one way or another nobody cheates and get away with it forever. I hope it all works out ok. Another thing you can do is go with him when he hangs out with her even act like your cool with her.