We love each other...I dont know what to do...?

I'm gonna try to make this as short as possible. I've been hung up on my ex of 3.5 years for almost two years now. He broke up with me and shortly after that I met a guy that I work with. It was like an instant attraction and we've now been seeing each other for a year and five months now. During this time we've never been an official couple with the title or label. I love him and he loves me and we tell each other that and I feel like it's time to move our relationship to the next level but everytime I bring the subject up it always causes a big fight. He refuses to put a title on us. He says that if I would just let it be eventually I can call him my boyfriend and he wouldn't have a problem with it. He claims that I'm the only person that he loves and the only person that he's sexual with. But he says he can't trust me and is constantly accusing me of stuff like getting with other guys and stuff. He thinks I'll leave him in a second for someone else. I dont know what to do. I love him and he's the only person that I love more than my ex. When I've tried to see other people I end up not being able to be with them because I can't stop thinking about him.

Please...I need a man's advice about this. Please help me.