What Happened??

Olivia • 22 years old, single momma 👣 Dominic A. was born April 28, 2016 👶🏼
I was originally EBF with my son, but as he grew I noticed my supply wasn't keeping up. We started doing both formula and breast milk, and I would pump every time he had formula. This worked for about a week, then it still was decreasing. I'm at the point now where he can feed of both sides for an hour each and still be so hungry that he can drink 4-5oz of formula before being full - and he's only 6 weeks old. I'm at a loss, I went from being able to feed him comfortably and still stock up a few bottles, to not able to feed him at all 😞 Why might this have happened?