Going back on birth control after having a miscarriage....?

been on birth control for 6 years, got off in january 2011 miscarried in late april, got back on in june. Now ive been havin cramps like im on my period, spotting here and there, and sore breasts. This never happened to me while being on the pill, im wondering if its just my body trying to get back on track? anyone else experience something like this?