Help!!! Breastfeeding Working Mom

I am having trouble with my pumping milk supply. I am a night shift RN and pump while I’m at work and breast feed my now 8 month old while I’m at home. My husband feeds my son my expressed breast milk at home while I’m at work. My son has been taking 4 oz at a time but I am only pumping 1.5 oz every 2 hours while at work. We are going through my freezer stash at a rapid pace and I’m scared we won’t make it to a year at this pace. Any tips tricks or advice to get my supply up?

Also any advice on maybe mixing my breastmilk and formula to make my freezer stash last longer?