I think you should trust your instincts and remember that he cheated on her when he started dating you, so to expect him to suddenly be a different person would be foolish.
I don’t advise that you INSIST he tell her about you or ASK HIM to tell her to back off. What you should do is decide if this is someone you want to continue dating, given that he’s not being honest with his ex-girlfriend, and probably not with you, either. 😳
I hope that helps. Let me know how things go — and follow me @AskAprilcom on Twitter, and on Facebook: [url][/url]. 😀