Why is it so hard to pretend like you dont still have felling your ex boyfriend?

me and my ex boyfriend broke up like not that long ago and i still have feelings for him he say he still likes me but were not on the same page also he already gotta gf why would i want to o back with him i think he just using me to get to something.(hes a player)i would like to go back with him if he would change he personallity but other then that were never gonna be