Why is my ex doing this..?

I don't know who broke up with whom, but he's clearly hurt. The best way he knows how to hurt you in return is to say those things about you. It's juvenile. It's ridiculous. You're soooo much better off not having him as a friend. People only say things that malicious if they are hurt and they want you to feel the same level of hurt. Let that jack go haunt some other girl.