I can't get this out of my mind

I was in eighth grade when i met this guy named Juan. He was 15 at the time and i was 13. We both started to like each other and eventually started dating. He would always ask me to have sex with him and i would say no because i wasnt ready and didn't want to do it at that age. But he just kept insisting, so i said ok to get him off my back. A few months later, we were at gym and he told me to turn around and he did it to me. I know I never said no but i didn't say yes either. This happened awhile back, but i cant get it out of my brain. I honestly feel like i just did whatever he said, because i wanted to be a good girlfriend but i was never comfortable with it. I have made a vow to myself that i will not have sex with anyone again until i completely trust that person and when i am more matured. I just need advice on how to stop thinking about it and move on.