Can I just say ONE thing? He got with someone else while he was with you, just to keep his reputation.
I got with my OH when I was 14, he was 19, and he wouldn't of got with somebody else just to 'keep' up his reputation, he loved me and no one else! And age didn't matter because of how much he loved me and I knew I loved him, we didn't care for other peoples opinions, they thought he was a paedophile, but he wasn't, it was love, I am 18 now and we are still going strong, we proved everybody wrong.
I think this guy is taking you for a ride, it doesn't sound like he loves you, it sounds as if he is using you and having fun with other girls at the same time, I know if my OH had of had another girlfriend whilst we were together we wouldn't of been together now.