I went through something similar with an ex-boyfriend. He was my first serious relationship & he slept with a girl that he worked with at about the 3 month mark. He said nothing happened, so I believed him, then later on he admitted that he slept with her but said he thought about me the whole time. I was devastated, but we kept going and stayed together for three years because I suppose I thought that we loved each other and should keep trying. However, it was never the same as I couldn't trust him anymore. He wanted to talk it through and I just wanted to forget it, which didn't help. It took a lot of hard work and sharing to even get back to somewhere approaching what we'd had before. That's not to say that we didn't have good times, as we did, but one day when he was away I woke up and realised that I didn't miss him and that this wasn't the man I wanted to be with and we split up. He said that he'd been about to ask me to marry him. Maybe, maybe not. But maybe it wouldn't hurt to have some time apart so you can think about what you really want.