*names have been changed for privacy*

so this happened a few years ago. I was friends with a guy, Marcus* who is a year or two older than me. we were friends, but we never really hung out much. he asked me to go to a creek near our neighborhood with my brother, Brian* and their friend, Daniel*. I went with them, and we ended up playing truth or dare. and that is never a good idea when it involves a ten year old girl and three horny pre teen guys. my brother and Daniel* did nothing wrong. My brother and I have never gotten along well, but we were getting along ok then, and Daniel* was a friend who was really nice and a good person. these two did nothing wrong. but Marcus* did do something wrong. he dared me to flash the people on the bridge in front of us. I didn't want to, but he convinced me to. so I already was uncomfortable, and then he dared Daniel* to say some inappropriate things to us, and by then I left. I walked home by myself, and didn't tell a parent or friend what had happened. fast forward about a month, I think. a friend and I shared a cat, who had recently gone missing. we later on found out that another girl who didn't like us convinced her mom that cat was a stray and to take it to be put down without saying anything or even asking. anyway, I didn't know this yet, so I was looking for her. I ended up walking around our neighborhood asking if anyone had seen her. I eventually got to the place where Marcus* lives. I asked him if he had seen a black cat, and he said he had seen one in a large concrete drain in the next neighborhood. somehow, he convinced me to go with him to this drain. I was riding my bike but he was on foot. when we got to this drain, I put my bike down and walked to the other side of it. Marcus* then sat on my bike and told me that I couldn't have my bike back unless I flashed him. It's easy him a firm, serious NO. he then continued to tell me to do it. I said I would go tell my dad what was happening and Marcus* said ok. I told him to give me my bike back, he refused, so I began to leave. he then hurried past me and left. I blocked out this memory without telling anyone. Then, at a birthday party at a park back in August of 2017, someone happened to bring up Marcus*, because he goes to our school, but he's not in our grade. some friends and I had gone off to a different section of the park from where the party was and played truth or dare. after a while, Marcus* was mentioned and everything rushed back. I didn't even tell anyone what happened, but told these friends that I don't like him, and that he was mean to me. then , in September, I went on a girls' lake retreat with some friends and girls from my church's youth group. we had a lesson on forgiveness, and i finally decided to tell a friend, Veronica* about what happened. I told her the night before we left the lake, and the next school day, she told her best friend, May*. I didn't mind that Veronica* told her, because May* was Avery close friend of mine also. after a while, I told two other friends, Hayley* and Emma*. I told them that I didn't know what to do. Hayley* told me to forgive and forget when I said that I kinda wanted to talk everything out with Marcus*. I never did speak to him, but soon he ended up being in a club that I had joined. I didn't know that he as in this club when I joined. three friends, Ann*, Jenna*, and Emma* were in this club with me. we ended up standing in a line behind Marcus* and his friends, and he happened to turn around and notice me. and he just stared at me. Emma*, who was one of the friends I told about him, stood in front of me because she knew I was uncomfortable. I've seen him looking at me other times. later on, I told Ann* that I didn't like Marcus*, but I don't tell her why because her brother is good friends with Marcus*. I still see him everyday at school, because he often comes into my fifth period classroom before the bell rings, and passes me in the hall often. I know that this is practically nothing compared to what other people have been through. but what happened has affected my relationship with guys. I'm even uncomfortable being alone with my dad or my youth pastor, even though they have done nothing wrong. I trusted someone, and this happened. it has really affected my life, and I already have anxiety among other disorders, and I think I may have PTSD. I don't want to tell anyone about what happened, but at the same time I want to tell someone so that this can all be over. I don't know what to do. please give me some advice!!