Talk to Gynecologist on Periods

I'm a breastfeeding mother. My baby is 10 months old. She is taking solid food as well so she is not totally on breastfeed. My problem is that I'm not having a periods on time My last menstrual date was 10 May. And till now my periods is missing . I was a patient of pco before conceiving. Now my question is that reason of my late periods is that I'm breastfeeding mother or should I go to doc as I was a patient of pco too.