feeding moms who suppliment with formula? (or any other mother) :)?

Ok I exclusively fed for the first 6 weeks... Upon returning to work I had to quit pumping because my were SOOOOO sore and it hurt when I was able to feed and it made me not want to so I just began formula when he was away and nursing him every opportunity during the day and and night... With that being said. I am 8 weeks PP this week and Aunt Flo returned... Just wondering when it returned for the others out there...