How often do women get pregnant while on the implanon? This is my second time on it, & haven't had a period. Last time, I had a period almost every month irregularly. I've been back on it for about 2-3 mo. Also I've been EXTREMELY upset and moody lately & my boobs have been sore.  I'm curious as to how much I should worry or if this is just the birth control doing this to me?