Well it sounds like he wants to have his cake and eat it too.....

It may hurt for awhile and you may feel rejected but if you give into his wishes now, you are setting yourself up to be the victim and that in the long run will hurt you more than letting him go now. Always stand by your principles and you will always come out the winner. He obviously isn't ready for a committed monogamus relationship like you are and although open relationships can and do work, both parties must be agreeable wholeheartedly at the onset of such to be sucessful.