Wait so in between the time you posted this thread, and the time gruesome posted you two seperated?
Anyways your both guys. Theres the problem. Of course he wants an "open" relationship, but hes probably just thinking open for him. Im sure he would get upset if you were like Ya, so Im going out on a date tonight with Terry, and his girlfriend. Then afterwards we're all going to take X and fuck like rabbits all night.
The only way you can have a serious, nonpainfull relationship is through commitment, trust and all that other crap. So either don't invest emotions and be open. Or put yourself into the relationship and let your feelings be there.