I can’t get sexual harassment at 17

every once in a while I can’t sleep over remembering my teacher sexually harassing me. He would lower his forearm when doing out warm up homework and graze his arm against my breast. I was even a sloucher and would slouch more to try to avoid him but he would compensate for my slouching. This happened toward the end of my senior year. I tried anonymously reporting it when it kept happening but nothing happened and despite me being almost done with his class, I dropped out. i felt sick when he would do it and would even run to the bathroom when it was homework check time. I still feel sick thinking about it and I don’t know what to do. would this be an email the school type thing? It’s been almost 3 years since it happened but I am only now getting slight strength to report it.