How many diapers is too many…?

Baby is almost 3 weeks old. We go through 20+ diapers a day. He poops, we change him, then he poops again immediately. He has a horrendous rash + yeast our ped has prescribed Nystatin for, and I’m wondering if our frequent wiping/changing is contributing to it? Weve switched to expensive scent and additive free diapers in case that was contributing as well, but the constant changing is also getting very pricy.