Can Breastfeeding And Being On Depo Shots Cause Missed Periods?

Hi I was wondering why i wouldnt be having my period. I Havent had a real one since before i got pregnant with my son who i gave birth to in sept. 08. I breastfed for bout 7 months and just recently got off of depo shot about 3 months ago. I still lactate if i make myself. I just been thinking between the depo and breastfeeding it kept it away. But now im starting to wonder.