On going diaper rash

Starting at 8 months my daughter got this bad diaper rash. The drs thought it was yeast so we treated for yeast. It never went away I have been to childrens express 4 times and the drs office 5 times. It has been 1.5 months now!! Ive been prescribed nystatin cream 4 times, lotrimin 2 times and then an oral medicine gone thorough all of them. I switched to new diapers and diaper cream to make sure it wasnt that. NOTHING is taking this away. Mind you EVERY single time we change her diaper we put diaper cream on her because she is so sensitive. Idk how this came or why and I cant get rid of this. We havent changed anything different. No laundry detergent, food, formula, literally nothing. Im seriously at a loss and I feel so bad for her my heart breaks. anyone else ever have this happen?!? How do you make it go away 😭 thanks mommas!