How do I explain what I feel

STORY TIME!

So guys I've been dating this one guy for a while now and he broke up with me telling me he was still in love with his ex so I accepted it and took it like the adult I am. He got back with his ex the next morning, I was very angry because he didn't give it a bit of time but I took it like an adult ever if it hurt me to them walking in the halls together. I saw them a few times since me and her have our college algebra class together I just took it never saying anything taking it all. But then he starts to talk smack about how I was a bad girlfriend because I like to party and I say bad words a few time's you know call people a bitch just playing and everyone knows that, then he says that I changed a lot since me and him got together. Like bitch I was getting all getting comfortable and showing you all of my true self and you leaving? Then I took that like an adult until I see him walking in front of my class when his class is in the other building and so is hers and they start to kiss in front of my classroom that is just so so so petty. Then he started telling people I cheated but I didn't I actually loved the dude. So  just took everything trying to be the bigger person. But now I'm all concerned about him because he got with her and his teachers who thought we still dated told me how they are concerned about him because he is failing them all and he need's to pass to graduate in May, then I see him skipping class and being like 30 minutes late along with that girl he quit his job his mom is mad at him and he isn't showing up to track practice and that's what paying for his college, a full ride that he is about to loose. I'm concerned because I once loved him and I wouldn't wish bad on him. And people are all mad saying I shouldn't be all concerned because he's an ass and how he's an ass but I can't help it. I think I'll write a book about this relationship honestly. 

WELL GUYS I WILL UPDATE SOON PROMISE I JUST HAVE BEEN SO BUSY AND STRESSED AND I'VE LOST SO MUCH WEIGHT SINCE HE LEFT.