If you reply then he'll reply back and you'll reply and so forth. It's not healthy to keep reopening partially healed wounds. Be careful because you might learn things you didn't need to know and get hurt worse. You can be just as hurt whether you slept with someone or not. If he was worth the effort than he'd have proven himself a long time ago. Sounds like he's playing with you.
If you can read this then you're standing too close.