Pill or implant

Christie
I had my second baby March 23rd and went back on the pill. Before babies and after my first I was fine. My period would start a couple of days after finishing my pack but since going back on it this time I begin bleeding a few days before my packet has finished? Any one have any ideas why? Also thinking about going on the implant but don't want heavy periods or to gain weight. Anyone got experience of this? Sorry for the long post :)