Manipulator and Boyfriend Problems!? I need Help! Please!?

Well what i am about to tell you is going to make me sound so stupid.. I sent a picture of myself in lingerie to my boyfriend(he is 17). Anyway, i broke up with him yesterday.. two weeks after i sent him the picture. Well..his friend GIRL 1 got his phone. She send me back that same picture with the caption "I have power - from the girl you don't want to **** with:)" (She is 18) And if i don't ask him back out again she is going to send that picture to Facebook, my friends and tons of other people. But i don't want to get back together with him! WHAT DO I DO!? PLEASE HELP ME!! :'(