he keeps dumping me then he comes crawling back why?

[Hayley]

so in the past my boyfriend has been really bad to me i have been beaten etc etc he's calmed the beatings down but now he dumps me every other weekend goes on a 3 day drinking binge then he comes back and hounds me harasses me with fake promises that change the minute he comes back. He follows me to the kids school to work until i give in and let him back.
I dont really want him i'm sick of his games but the way he harasses me its easier to take him back then a few days later he's gone again. he left this morning again after the usual you fat and ugly and i hate you comments i dont call him when he goes i just ignore him and get on with my life why if he hates me so much does he come back? what is his game?