Supplementing with formula

My baby boy is 8 weeks old. He doesn’t seem to be gaining as much weight as he should. I will also be going back to work in 4 weeks and I don’t seem to be able to pump enough to keep up with what baby will be eating at daycare. I have tried lots of different products and strategies to increase what I pump, but none have been successful so far. So unfortunately it seems as if I will likely need to start supplementing with formula. Of course I will be discussing with our pediatrician, but I’m just looking for some input from other moms.

Do any of you ladies supplement? What formula has worked well for you? What kind of feeding and pumping schedule do you follow?