need answers !!

I received my last depo shot in September 2016 and missed the one in December 2016 I had unprotected sex with boyfriend in January could I be pregnant? My last period was in December too and still haven't came on yet ? Could i be pregnant? I'm always in the bed , sleeping a lot and not eating as much as I was , I started talking the prenatal pills last week and I had light brown spotting.