What is going on with my ex? I need some advice?

Ok so me and my ex broke up after 8 months ..but he broke up with me for another girl..a month went by and he ended up cheatin on her with me..we had plans on getting back to gether but it never happends...he tells me how much he still loves me and cares for me...but i dont get it? if you loved me that much wouldnt you be with me..? he cheats on her all the time with me..so i stopped seeing him because i figured he was usuing me..but he still makes efforts to text me all the time saying he cares and flirting..what is going on with him? im heartbroken he left me..and with him still telling me all this stuff hes messing with my emotions..i need some adcice thankss .