Please help. Baby’s rash won’t go away 😩

I desperately need help with this. My son is 9 months old and we’ve been dealing with this rash for 2 months now. This is mild compared to what it will look like in a few days. At first, the doctor said it was eczema. We switched to non-scented detergent, soaps, etc. It didn’t go away. Then they said it was a yeast infection. We tried lotrimin, nystatin, and ketoconazole. Nothing helped. Then, they prescribed hydrocortisone cream. It went away overnight. We used it for a week and stopped. Then it came back within two days of stopping the hydrocortisone cream. They told me to use it again to clear it up, so i did. Now, it’s back again and looks like this. Within a few days, it will spread to his thighs and be very itchy. I don’t know what else to do. We change his diaper as soon as we see he’s wet, we use diaper rash cream during every diaper change, we’ve tried aquaphor, eucerin, and aveeno. Nothing helps except the hydrocortisone cream but i do not want to continue to use it because of discoloration and skin thinning risks. I’m at a loss. Please help!

UPDATE: thank you ladies so much! Changing the diaper brand is the only thing i didn’t do. I tried a few different brands, and nothing helped. But then I gave in and bough the more expensive Huggies Special Delivery. They’re hypoallergenic. Overnight, the rash is gone!!! Thank you all because I never would’ve thought to switch diapers since we’ve been using pampers since birth with no problems. I guess he just developed an allergy around 6 months old!