Search Results: ex marrying a friend

I'm 17 and my boyfriend is 19. We have been dating for 3 months and are in a long distance relationship but see each other at least once every month. March 9th will make 4. He keeps in contact with his exes and it bothers me. He even said that if she needed help, he would tend to her. Recently we had a dispute over him going to another County to help a "friend" of his out. She's a girl and he says that they've never dated. I don't believe that. He even said that they made a promise years ago that if they were not married by a certain age, they would marry each other. She's pretty much been around since the beginning of our relationship and still is. I never knew about her until the argument we had over him going to "help" her. She locked her keys in her car but yet she has a boyfriend. Why couldn't her boyfriend help her? He even went as far as calling her his Plan B! He said he loves her as a plan b. I don't know wtf that means! I feel he doesn't care about our relationship as much as he says he does. Is there something he's hiding or not telling me? I feel like I know an my gut is telling me he's not worth it but my mind wants to wait it out. We even say I love you but at times I question him about it. He's also having a party on the 20th and his ex is attending. I will not be there. Please help