My ex boyfrind and some chick !!!! wat do i do?

okay.... after me and my ex b/f broke up there was this grl that he liked and all and she told me yesterday that he talks really bad about me in class like a DOG!!! and i havent spoken to him for about 4 weeks now and she says that he dosnet want me and he has a grl friend and she told me to GET OVER IT!!!! but should i belive what she says b/c she's made up a lie on me before....!!!!! and every now and then i'll ask him dose he still like me and he'll say a little so what is she talkin about what do u think i should do