first pp AF already?

I went in for my 6 week check-up today, and my OB thinks I am getting my first pp period. I had a lot of bleeding pp but it had decreased to spotting by the beginning of this week (still definitely required a panty liner). Then two days ago, I started having bright red moderate bleeding again.

My daughter had only had breastmilk until last saturday. Before then, I was mostly BF but giving pumped milk in a bottle once every other day or so. Then this weekend I had a meltdown and decided for the sake of my sanity and nipples that I needed to be able to give her bottles more often if necessary. However, last week I learned at a lactation support group that she took 6oz (!) from the breast at a feeding, but I can only pump 3-4oz. Also, I will not be able to pump when I go back to work in June, so we felt that it was a good time to start adding in a bit of formula (1-2oz.) when we wanted to give her a bottle. I have continued to BF about half her feedings, and I always pump if she gets a bottle.

Sorry this is so long, I just didn't expect to get my period so soon, especially since I still BF or pump every feeding, and it makes me sort of sad. I feel disappointed in myself for some reason, like my decision to pump more feedings and supplement makes me a bad mom and now I'm getting AF and my supply might tank. I haven't noticed a change in my supply yet, but I'm worried about it. Anyone else get it so soon while BF?