he keeps dumping me then he comes crawling back why?

[Kittysue]

Because he knows that no matter what he does, you are weak and have no self esteem and will take him back. Abusers look for easy victims they can continue to abuse. Each time you let him back, you tell him it's ok for him to abuse you and he will keep coming back
You have to cut him off completely - dump him, change your number, change your email, block him from social media and make sure your profile is private, move if you have to. You have to completely cut him out of your life and make sure he has no way to contact you. Do not take him back - he's just looking for an easy outlet for his anger and hatred and you give ti to him
If he loved you, he would never be abusive to you. He hates you and sees you as weak and pathetic and feels he has the right to keep abusing you