Ex Troubles

My boyfriend of 2 years broke up w me a little over a month ago & the next day he was hanging out with his ex(who got into our relationship & told me to not worry about her) a couple weeks later they were dating! It’s been a hard pill to swallow, because of what he said to me about her and what she tried doing to our relationship & the day before he broke up w me he said he still sees a future w me & then we got into an argument about THIS EX & he straight up told me the next day that he wasn’t happy w me anymore and didn’t love me anymore & we didn’t end up on good terms. Well, I started hearing rumors going around the school that I had sex w this other guy(which is very untrue) and I usually don’t care about these kind of things, but it was never going to end & she was the one who started it so I texted her to stick up for myself and just said that I’d appreciate it if she would stop running my name like she was running her mouth. It wasn’t anything rude or anything that would jeopardize their relationship, it was simply just a stop talking behind my back text. The next thing I know I get a very rude text from my ex saying all this stuff about how happy he was and how he cant believe he spent all that time w me & so many more things, I didn’t say anything back, because I thought it was ridiculous, but I just need a piece of advice or just someone who’s been a in a similar position as this to tell me how they coped w something like this, because it’s starting to take a toll on me. I just have so many questions that I will never be able to get the answer to.