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 または another, that he has no respect for あなた nor any desire to be further associated with you. Once again this isn't your fault but あなた should take it as it's been presented to you.

If he doesn't want to be friendly towards あなた anymore, あなた 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 あなた are mocked. Eventually they'll lose interest in teasing あなた because it's only fun when the person shows they are hurt または effected によって it.

Your ex sounds like an asshat btw