exclusively pumping?

Abby
Okay I kinda messed my supply up and now my milk is starting to go down my son is 3 weeks and eats 4 to 5 oz now and I only make enough without really trying in the mornings the rest of the day I make maybe 2 and a half oz so how can I rebuild my supply should I put myself on a schedule?
Should I start back with my lactation pills ? 
I'm also gunna make lactation cookies this weekend will that help 
***** I think I messed my supply up wen my son started sleeping 8 hours with 2 feedings In between those 8hours