Sweetheart - you really need to end things with this guy and find someone (a) closer to your own age and (b) without the baggage. From what you're posting - he is still married. Which means he's committing adultery, with a 17yo child. It doesn't matter if they're over (obviously, they're not THAT over if he managed to pass her STDs to you - unless he got them elsewhere and gave them to BOTH of you), blah blah blah. He's cheating on her. He cheated on you. What on earth makes you think that he won't cheat again? You can do so much better than this for yourself. If he was that committed to you, he'd be showing it by acting like a man does. He's not doing that. Cut him loose, or you're going to be in for a world of heartache in the future.