It's normal for BF mothers to have menses. I'm a working mom too and only nurse my boy after work and on days I dont't work. I had my first menses when my boy turned 6 mths. But it was very light and lasted three days only. And my menses is irregular now. Before pregnant, my menses was very regular. My boy is turning 9 this month and so far I had my menses twice. Before you have your menses, your supply will drop a bit due to hormone changes and it will be back to normal after menses ends.. Just pump according to your daily routine.