3 weeks post partum -- period returning?!

Hi ladies! Exactly 3 weeks post partum.. Had a c section woth my second baby, after which i bled for 6 days (the last 3 of which were extremely light). Have had NO bleeding since. And yesterday afternoon I started bleeding again, brown but period like flow with cramping, a persistent headache and increase in appetite. I'm pumping exclusively every 3-4 hours and getting about 4-6 ounces of milk each side every session. Was wondering if this is just still post partum bleeding that has come back or if my period is back?!