I sat on a secret like this for a year before I blurted it out at a most unfortunate time. I kept my knowledge to myself because I had much bigger stake than a two-year boyfriend, though.
I don't think you can keep this sort of thing to yourself indefinitely, and quite honestly, I don't see what motivates you to hang in there with him if you don't have any children (or other significant complicating factors). Life is short; don't waste your time. And for the record, he is definitely NOT what every girl wants. He's been cheating on you!
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?