Replying to Ex girl friends a slut /rant

so me and my girlfriend broke like a month and a bit ago but we still were talking and stuff , so like 2 weeks ago she invites me over to her house because our school was doin staff vs student volleyball. so i go over right cuz im stoked and still really like her and then one thing leads to another and we end up in her room ( no need to explain rest ) so now im stoked on life cuz i thought she was still into me , but nope next day i find out she is all over some other guy and found out last night that they hooked up a week after me and her , and now i just pissed i dated a slut for almost a year and a half / end rant