Relationship is falling apart.

I have actually had a simular situation, so I may be able to help a little. I'm gonna try to keep this as short as possible, but that may be difficult because I am a rambler. So when I was about 17, I had been dating this guy for about 4 years, and what started as a cute little 13 year old relationship actually turned into something bigger. He was at that point the love of my life, I thought I was going to be with him forever. Me and his friends were kinda close, they were my friends too, and I hung out with them before. But one night I went over to one of our friends house to study for a test I had the next day. When I get there, he tells me he has always liked me, and then he pins me down and kisses me. Of course I reacted like anyone would, I pushed him off of me, and I got up and left. That didn't make him happy, so the next day he told everyone at school that we had sex. My boyfriend actually heard it from one of his friends, and he wouldn't talk to me for   a long time. Then he came over and I told him what happend, and then eventually the guy confessed that he lied. And we were together for about 3 years after that and the only reason it ended was because he left to go to college, and we eventually just grew apart from eachother. SO, my advice is to give him time, eventually he will come to you for you to explain yourself, then tell him what happend, if he doesn't believe you then it wouldn't have worked out anyways. Relationhips need trust, if he doesn't trust you, it's not a good relationship.