I am so sorry that this is happening to you. Even though I don't you, I can feel your pain. It's not fair, is it? On your question, speaking of what I would do, I would have to tell the truth. It will come out eventually so it is better to tell him now before you or he falls head over heals. Also there is the responsibility of "safe sex" and caution. I can't advise but I can tell you only what would be right for ME to do. Donno if this helps but what else can I say.