Breastfeeding help

Ca

I have a 4 month old that I breastfeed. He gets some formula at daycare because I can’t pump enough to keep up with him. When I feed him he seems satisfied and his dr isn’t worried about his weight so I’m assuming he’s getting enough milk from me. The last week though I have been pumping less milk. I’ve never pumped a ton anyway but now it’s even less. Is this normal? Is my supply going down? Or is it just because I’m pumping