But if you let him go it won't be because of her, it will be because of him, his immaturity, his big mouth, his poor boundaries. If you think he's really great then accept how he is and know all your business will be out there. Or have a really serious talk with him and let him know you will leave if he keeps telling your business to her (and likely others). I could see sharing some things with a best male friend, but an ex? And as some have said, perhaps he is just an oversharer and it's all innocent. But it sounds like he is very immature and he and she are playing games, and that neither he or her can be trusted. I tell you one thing, I would definitely not be intimate with him until this issue is fully resolved.