I wouldn't be too worried unless you're feeling pregnancy symptoms. Your period should return in the next couple months I would guess. I only breastfed for about a month and my period didn't return til 4 months postpartum.
I would not worry too much. I had my son December 27th and did not breastfeed and got my period 7 weeks postpartum. Most women receive them within 13 weeks if they are not breastfeeding and months if they are.
I have daughter born on Dec 21,2015 also :) Best wishes to you and your sweet girl ;)