Three week old not gaining weight

My lo was born Aug 6, weighing 8.1lbs, at 3 days old he was 7.11, and at 4 days old 7.1. At this point we started supplementing with formula- I also had a spinal headache that was fixed via blood patch at 6 days old.

In one day he got up to 7.5 with supplement, we went back two weeks later, I had stopped supplementing after 3 days because my milk came in. At 16 days old he was only 7.8lbs

The pediatrician is giving it one more week to see if he will gain at least 1/2 ounce a day.

He eats 8-10 times a day, has at least 6 wet diapers a day and poops 2-3 times a day.

I don’t understand why he’s not gaining better.

I’m doing breast compressions, feeding on demand, eating Lactation cookies, drinking a chocolate shake with fungreek and other milk booster, drinking Gatorade and lots of water.

I can also pump an additional 1-2 ounces after nursing.

Any insight? Advice?

I do not want to go back to supplementing again.