How do i talk to my mom about this guy??plz help!plz?

hi im 14 and my mom has said "no new boyfriends for the rest of the year" ive only had 3 that she knows about but still. and now im in a relashonship with my ex and my mom knew him all my frmily did but he broke up with me for the second time about to months ago. but now we got back to gether for the 3rd time. the frist time was only like 4 days though. and i know its going to last this time we wer together for 2months the 2nd time. but i dont know how to tell my mom im with him agin.i mean she is the one who saw me crying the night he boke up with me and the next day when i couldint to go to school so its going to be hard to tell her. so what do you think i shold do to tell her?? cuz i know its gana last this time so i cant keep it from her and me and him go to difrent schools so we have to hang out on the week ends. thanks so much for enything right now cuz i realy dont know how to tell my mom about this guy.