Decrease in milk supply

Zena

My LO was born at 33 weeks and was in the NICU for 2.5 weeks. Everything was going great with pumping and I was able to take plenty of milk to the hospital for him and they sent some home with me. However, I have been having trouble producing much lately. I haven’t been able to get more than a total of 55mL when pumping for the last 2 days & he should be getting at least 70mL for each feeding. What can I do to increase my supply asap?