How to increase milk supply?

What are some tips or advice to increase breast milk? I’ve noticed when I pump, sometimes I can’t even pump once. Once in a while, with both boobs together, I can pump a 3-4 oz. But when I nurse, it seems I’m able to release more than I pump, like milk flow is there & dripping. I will hear my child swallowing & when it is done, nursing milk when be coming out by the side of their mouth. I’m not sure if it just when I’m pumping, my body not taking it well as nursing. Has this happened? If so, any advice/stories. I’m four weeks postpartum.

3-4oz when 4 weeks pp is a really good amount to pump and totally normal amount especially when feeding at the breast aswell! I only ever pumped around 1-2 oz per breast unless a feed was skipped