Supplementing

So I’m a FTM and my son will be 3 weeks old tomorrow, I recently started going back to school and I noticed a few days ago I haven’t been able to get much breastmilk from pumping - maybe 2 ounces after pumping throughout the whole day (I was able to pump more last week for school) I’m gone for class, including drive time) from 9am-1pm & 4:30pm-8pm on Tuesday, and then 9am-11:15am on Thursday. I was wondering if it would be okay to supplement with formula while he’s home with his dad after he goes through the BM I am able to pump? He does fine at the breast, it’s just the pump I am having problems with.