How do I get over trust issues because of a bad experience

Hello ladies, so I'm 16 and lost my virginity at 15(a month after my birthday). It was my first proper boyfriend and we had gotten together 5/6 months prior. I know it was so rushed and I regret it so much but I can't change it now, it was ridiculous. We were together for about 9 months and then broke up for a while; but remained on and off for a year and a half. We were still sleeping together and stuff too. Things turned nasty and he actually slept with two other girls to spite me, one of my friends and a  girl that later became a friend knowing what she had done. While I was seeing him they were 'best friends'. We haven't spoken in 2/3 months. I've now heard that he is spreading rumours about how bad I was in bed and what I liked and stuff, but none of its true. I kept everything intimate that happened to myself and didn't tell anybody, and there is so much I could say to get him back but I'm not a spiteful person and despite what's happened don't want to hurt him. The little self confidence that I had is completely gone and I just feel stupid and down and used when I think of what's happened. I am over him, he's not worth wasting time on, but it's how I feel about myself. I feel ruined and I'm still young, wish I'd kept my legs shut. The thought of ever being remotely intimate with a guy again terrifies me, but I do like somebody for the first time in so long.