Really bad diaper rash !?

This is the first time I’ve ever dealt with diaper rash, my baby is 4 weeks old and it started 6 days ago. The actual rash itself has gone away but then he has these blister looking things on his bum that have been there for about 5 days, they have gotten worse but now I feel like they’re getting a little better.

I’ve been letting him air out with no diaper for 20 minutes every changing, changing him at least every 2 hours, putting diaper ointment on it, and wiping with a warm wet washcloth.

It still isn’t getting much better and I’m very worried at this point....