Milk supply

I'm 3 weeks PP today and I pump everyday. Never missed a day but I have been getting lazy and pumped less than 5 times for about 2-3 days and since then my milk supply has decreased so much. Are there ways any of you ladies have increased your milk supply? I know I'm supposed to pump every 2-3 hours and I'm back on track of doing that and I've also tried lactation cookies but for me they didn't seem to help much.