Stopping breastmilk

My son just turned six months and in the past few days my already low milk supply has dropped even lower. I have no idea why. He has started on solids recently, but I have been exclusively pumping since he was a few weeks old, so introducing solids shouldn’t effect my supply. At this point I’m thinking of just weaning off pumping and switching fully to formula. My original goal was to make it to six months, and he’s been supplemented from the beginning so I shouldn’t feel any guilt, but for some reason I still do. Anyone else in the same boat?