EBF switching to pumping

My 4 month old EBF baby has been on a ventilator in the hospital, sedated for over a week. I have been pumping round the clock so they can feed him through an NJ tube. My supply has dropped since I started pumping instead of BFing. I’m not sure if it’s necessarily from the pumping itself, the stress of the situation, lack of sleep, etc. The less I pump the more stressed I get and the cycle continues. I’m desperately hoping to return to BFing when my baby wakes up and recovers. Please, pumping moms, tips on increasing supply, pumping tips, anything to help. When my baby wakes up I want to be able to offer him breastmilk and the comfort of nursing. I need to do this for him.