Please Answer-What The Hell ? How Could He Do That To Me ?

When a person, in particular an ex, mocks you, it isn't your fault. This sounds like an incredibly juvenile situation and it should be viewed as such. He has made it known in this instance, for one lame reason or another, that he has no respect for you nor any desire to be further associated with you. Once again this isn't your fault but you should take it as it's been presented to you.

If he doesn't want to be friendly towards you anymore, you should wash your hands of him. He appears to be going for childish teasing anyway. Roll your eyes at his antics and don't respond with much care when you are mocked. Eventually they'll lose interest in teasing you because it's only fun when the person shows they are hurt or effected por it.

Your ex sounds like an asshat btw