Reduced breast milk

Hi ladies I’m into my 10th week of expressing for my premature baby. I had a very good amount of milk so was advised by nurses

To only express 5-6 time a day which I have been doing for a while.

Last few days I have been off

Routine but today noticed my milk supply has reduced slightly. How can I build this up or can I build this up?

I mentioned to the nurses my supply has reduced they disregarded it saying I have enough to feed my baby for now. She’s only on 8ml an hour 🤦🏻‍♀️

Any advice would be great!!!