How can I get over him?

ok, so my boyfriend broke up with me in SEPTEMBER. it’s been way too long..I mean it’s almost february. I can NOT seem to get over him, I’ve gotten over other boyfriends pretty easily, but he was the only one that I truly loved. I’ve had two boyfriends since him, one of which im still dating..and I really dont feel any connection with either of them. to make matters worse, my ex is dating my “best friend”. and they’re “sooo in love”. sighhh. I find myself crying almost everyday. and it’s NOTHING like me! my grades have fallen from A’s and B’s to D’s and F’s. I usually dont show much emotion, and my mom always called me the one who was tough and never needed help with anything..but this time..I NEED HELP. I cannot get over him and maybe it’s because he was my first love, but I cant get stuck on this because it’s really affecting my grades, and friends, and everything else I do. im just sad all the time. and my best friend talking about them being together doesnt help much either. …soo basically, how can I get over him?!?! any suggestions as to what I should do at this point? I would really appreciate it.