It’s sounds like you have problems with trusting him which I don’t blame you. It’s hard enough building a relationship when he seems unsure of what he wants, but it’s a double whammy when there is no trust within the relationship. Have you sat down and discussed your feelings with him? And I don’t mean arguing, but talking about how you feel about him and how he feels about you. Trust and communication are very important aspects of any relationship; if you don’t have them, you’re in for a rocky road and a dead end relationship. I’m not sure how old you are or how long you have been in this relationship, but if it’s truly meant to be let him go and he will return. From past experiences, I would tell you to attempt to discuss your feelings without arguing. If that doesn’t help, then you both need space to figure out what you both want in the relationship. Once you opt for space, make sure you give him space, don’t attempt to contact him. Let him contact you. If your love is meant to be, he will come back. Even though he has caused the rift in the relationship with his ex, you will also need to work on your trust issues if the relationship is to work. It’s very important that you truly feel in your gut that he’s seeing her and not being a little paranoid yourself. When I was 18 years, I was in a relationship that resulted in a child. I tried my best to make the relationship work for the sake of my child. Well, in my gut I knew he had been messing with one of my so-called friends. I hadn’t heard anything about them through the grape vine, but it was just the funny way they acted around each other that gave me a clue that something happened. I didn’t know how far it went, but like I said, I knew something happened. One day he called me and going by my gut feeling, I said, “i know about you and ***, how could you do this to me.” I didn’t say when, where, or what since of course I didn’t know. He attempted to deny it at first, but I was persistent about him lying, I knew he messed around, and I couldn’t believe he would do this to me. He finally told me the truth. I ended the call with, “you’re such an fool.” remember, no matter how upset you get, keep your cool. I hope all works out for you, either way the wind blows; I wish you all the happiness in the world. Take care.