Why does is ex not leave him alone?

i was in a similar situation a while ago. my Boyfriend has had many girls in the past. he went back with the same one on and off for almost four years. he was in his senior year when we met and started going out I was in my junior year. the Ex who cheated (we'll call her Jane) started dating his best friends brother. when ever I went over there with him to his BFF's house and she was there she would wait for me and her boyfriend to leave the room then flirt with my bf. I over heard it one day and got really upset. I talked about it with my boyfriend and he didn't even realize that she was flirting with him. but Jane broke up with our friends brother because she cheated on him and everything went back to normal.
but I think in your situation if he was gonna leave he would have. but I think he was tired of being cheated on and that's why he left her. just talk to him and tell him your feelings and he'll do something to it.

Wait you have some serious things you have to think about here.

You and him have only been dating for 7 months and you are getting married?! That's crazy fast! And by the look of it it doesn't seem like you trust him. How can you marry someone you can't trust. I have one failed marriage behind me and I don't think you shouod be getting married yet, it's crazy if you have trust issues now marriage is NOT going to change that at all.

Also you have to ask him how he feels. If he is still having feelings for his ex then it isn't fair for you. I'm sorry to say that but it will hurt you more later on. Also maybe he isn';t in love with her and everything maybe he just feels scared about marriage but you have to think that he had an 8 year relationship and was never married why is he so ready so quickly now? I would say you definitely need to talk to him. And postpone this wedding idea until you are completely sure that you trust him. That kind of trust can't be built in 7 months but over a series of years. But that's just my point of view I hope everything works out for you.

Oh and on the ex factor chances are that she isn't even thinking about you or your feelings. She probably isn't even trying to hurt you, all she is thinking about now is that the man she thinks she loves is about to marry someone else, sorta my best friends wedding you know? So I guess it's nothing personal.