Guys, do cheaters ever change?

i havent been cheated on but my ex is having problems with his current gf (guess shes not giving him the sex since he wants it from me) basically we broke up (not long relationship) because thats basically all he wanted. originally he wanted more but ended up being just the sex and i wanted a relationship so it wasnt working out. i guess im still hung up on him 5 months later because he was my "first". even though he has a gf he has come to me more than once asking for sex. but i said no because i know ill fall right back for him and thats all he wants. he knows how i feel and that id go back with him but he told me he cant promise hed go back to me or her, tells me he just gonna use me for the sex and go back to her. should i just give up and realize he will never change or hope that he will realize how much i have to offer him and come back? it sucks falling for assholes sometimes :/, guys have you ever cheated and never done it again? reason im asking is he hasnt cheated on me whe nwe were together but if hes looking for sex from me and still with her, obviously he doesnt care about cheating and who says he wont do it if he came back to me...do guys ever change (at least the assholes lol)??