How can I get over my ex for good? It has been 5 years but I still can't stop thinking about him?

My ex and I began dating when we were in 8th grade and were together for 2 whole years. When I was a sophomore in high school, however, I went to a party with a bunch of seniors who offered my ex-boyfriend and I some alcohol and I decided to drink with them even though my ex begged me not to. I got so drunk that I ended up sleeping with one of the seniors and when I realized what had happened I felt so ashamed and guilty. My ex found out the next day and when I tried to talk to him about it I found out that he had removed me and blocked me from social media, etc. I tried creating different accounts on social media to be able to talk to him but he would always end up blocking me. I lost all contact with him for good and I haven't spoken to him ever since. I never got a chance to apologize or explain what happened. I am now a junior in college and I still can't get over him! I can't listen to music, watch movies, or play video games without thinking about him. I also tried to date other guys but my ex was always in my mind. I can't even be intimate with my current dates because all I think about while doing it is my ex. I haven't looked at his social media in a couple of years, however, I did take a peak two days ago just to see how he is doing. He is in a relationship now and seems to be very happy, so I don't want to try to add him again after 5 long years because there is no point on opening up old wounds. I just want to forget about what happened and I want to get over him.