Why do I stay with him? Can he change?

[Sophia]

I've been dating an ex marine for about a year now...he's 25 ,I'm 21. In the beginning of our relationship he was on instagram flirting with other women, looking up teenagers and on live jasmine searching "teens". I catching him staring at females all the time even though I told him how I felt about it.all of his marine friends cheat on their wives and call them "bitches". I've found pictures on his phone of a female he's never met before (he downloaded them off her facebook profile).

He's always making fun of big people when he's not even skinny himself. The other day we got into an argument and he said that I was acting like a dumb *****....he lies a lot..sometimes to the point where I don't even know when! He tells m that he wants to marry me,he loves me, and that he has changed and when It try to leave him,hell take something of mine so I have to come back.. he makes me look bad and tells our business to his" female friends".

I honestly don't find him attractive..he's overweight and eats very unhealthy and I feel nothing when we have sex....but I'm afraid to break it off ? Advice?