I have feelings for and slept with my best (guy) friend...now what?

Ive been working with this guy (im a girl) for almost a year now and since we started working together, we have been inseparable. Our co-workers even make bets on whether we are a couple yet or not. Ive continued to tell them that I dont have feelings like that for him and that we are such good friends I couldnt contemplate more. The truth though is that hes amazing we get along so well and have great chemistry. We slept togther for the first time 3 weeks ago and it went horribly because he came almost instantly TWICE. things weren't wierd at work, but he became a lil distant and avoided hanging out with me. I thought it was cuz he was embared. Yesterday, we spent the whole day at work together and the rest of the night together and ended up hooking up again...this time was perfect :) I dont know how to act around him at all now. I want to be in a relationship but im not sure if he does also. If i tell him this, I run the risk of ruining work and the friendship.Ne advice?