Breastmilk supply gone waaay down

Before I was filling two 70ml bottles from my right breast and about one on my left when I pump (I exclusively pump because my daughter was a NICU baby and we need to know exactly how much she’s eating.)

Over the past few days I’m barely getting 70ml combined with both breasts after pumping fit 20-30 mins.

I will admit since my daughter came home from the NICU I have been slacking on my pumping schedule of every 3 hours to pump because I’ve been so exhausted, but I haven’t strayed from it THAT much.

Why would my supply be going down so much and how can I get it to go back up? I really don’t want to lose my supply ☹️