What is happening to my Period....?

Okay I need help.. I am 14 and i have been having my period for over a month already since 4/11/11 and today is 5/17/11 and its kind of weird because i have very unregualr periods like i mean before anything i used to get my periods like 4 times a month or around that. Well, on December I was on birth control till march I got a shot named Depo Prov-era(its a birth control shot)I really don't know why i got it if i was still a virgin then a incident happened.. but yeah, I guess my mom wanted me to get it because i guess she thought i was a whore or something but anyways i have been to the clinic and all they have told me is that its normal and stuff but I really don't think its normal at all.. what should i do? or what do you guys think it is? :/