Why would my ex bf do this?

He texed me loads of insultd and I just say "ok" and he dosent get that I don't care what he thinks. At the end of the text I said "bye" and he said "hahaha ur so weird" THEN a day later, he called me and when I picked up he Hung up. Wtf. Then he texed me soon after saying "you sound ugly as s*it" so I said "ok" he said "bye" I said "bye" ThEn, hours later he called me (after he's been drinkin I think so he would have the to say ish to me on the phone) and started saying I'm ugly and stuff.. so I hung up......why did he do this, I'm worried I will have to keep putting up wit his bs. WHy is He doing this??? I don't care what he thinks of me just wondering why he's been an a**