well im stuggling with this issue as well. im dealing my mans exgirlfriend constantly being around. i was jealous of her because she had what i was having now and the fact that she got with him after we broke up the first time bothered me as well. i try to get over it by telling myself that you know i have him now and he loves me. then the whole issue of did he tell her he loved her the way he tells me he loves me comes into play. your only hurting yourself when you compare your resent relationship to his past relationships or hers sorry.
stricktlydating is right you should talk to your partner about any trust issue your having. conversation is key. i wrote a hub about it literaly called Conversation is key. check it out. it may help
~whispers of faith