I'm 15 and just had a 3 sum

Alicia • Love, Peace, and Tranquility
So a week ago my special friend decided to end things and go off with this in coming freshman (he's an incoming senior btw) anyways so I was pissed and lashed out so I had sex with his best friend, his best friend and I started talking more and then he brought up having a 3 sum with one of his friends that I didn't know, I was down for it at first but then it didn't seem like a good idea anymore, so that passed but then tonight he texts me and says "hey me and ty and er wanna hangout and I was like ok come over", turns out they wanted to have a 4 sum! And I wasn't ok with that but they talked me into it and so I started off with the best friend of my former special friend and then moved to ty but he couldn't get hard so I moved on to er and then all of them except for ty kept taking turns over and over and over again untill they finished after they were both done they said "ok we're gonna head out see you later" and left.....I feel so used and I know I could have prevented it but they are all so much bigger then me and I didn't know what would've happened if I said no.