im on the injection and have been having un protected sex with my boyfriend, the doctor mentioned that a side affect may be not having a period . if i dont get my period how do i know if i get pregnant? i know the injection is very effective but this worries me, as you get it every three months, itd be too late to do anything about it if the doctor noticed something. anybody else in the same boat? any replys on the subject would be great. o.O :$