My ex boyfriend wants to fight my current boyfriend!!!!?

So my ex broke up with me because he thought i was cheating. 2 weeks later no contact he says he wants me back i say no know he calls me a *****, hoe, etc. Now I have a new boyfriend (i had 2 after me and him broke up but he didn't know). Now he knows and hes like "WHO THE FUC* IS HE?" or "IM GONNA KICK HIS AS*" or "YOU AND HIM ARE GOING TO BE OVER." WHEN HE HAS A GIRLFRIEND I told him "you have a girlfriend , i have a boyfriend were both happy why are mad that I have a boyfriend? Are you not over me?" He said "I am." Then know he won't reply. Why is he doing this?? Btw were 14.