Help! Sudden low milk supply!

My baby boy is 11 weeks and I’ve been exclusively breastfeeding. This last week I’ve had a few days of sudden engorgement, so I’ve started pumping here and there. I was able to pump 10 oz from one breast! And 4-5 on the other. He will feed every 2-4 hours at a time, but with his longer sleep stretches he’ll go 6-8 hours through the night.

But as of today, I tried pumping and only received 1 oz from both breasts TOTAL. And it was an hour after feeding my son.... then I tried in the afternoon and only got another 1 oz... help! What is going on? What can be done to increase breast milk supply?