I need to move on but i dont know how...

my ex and i are still seeing eachother and have been ever since we broke up. all i am is nice to him but he treats me like a dick and when i ask him about it he says its just the way i am and that he cant help it. i buy him stuff and i let him borrow things and he still treats me like that. he asks me over to his house to well you get the point and i just cant say no… i need help really bad cause all he ever deos is make me sad and upset.. i dont deserve this but i cant seem to let go.. please help me! :(