I'm sorry Technicandy, but you cheated with this man it seems to me... that is really too bad as it causes a world of trouble and often means that things are strained afterward as people who are cheated ON have very strong feelings of betrayal and disrespect. Your consenting to his advances because he made the first move is meaningless here, as you CONSENTED. You had a chance to back down at that point and you didn't.
I would be very wary of this being a casual fuck for him and not a chance for happy romance. Call me a skeptic, but it could happen... especially as he has now cheated on his partner. This could of happened for a number of reasons, curiosity in that you are female, because you are cute, he thought he could get away with it and he knew you think he is hot and thought it would be a boost to his ego to seduce you... all of these things are very different when there are agreements in place, rather than no agreements in place... do you know what agreements and boundaries they have negotiated?
I would suggest reading here and seeing what you can find to educate yourself. I think that talking to your friend is a good idea to find out where he is at, so that you can assess what will happen next. You can certainly tell him how you feel, but if there is silence and then a whole lot of ignoring you that follows? I would be pretty sure you were a booty call and that was it.
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