• Diaper rash or infection?

My son will be 3 weeks old on Wednesday. He was peeing through Huggies diapers so I switched diapers to pampers and he broke out with a diaper rash around his legs where the diapers rubbed, the pubic area, and his butt cheeks. I switched back to Huggies. He now has been getting big, yellow, pus-filled blisters or boils. I don’t know if it’s just a diaper rash and needs an ointment with zinc applied or it is an infection like staph, MRSA, etc. he has no fever and has no other symptoms except fussiness.