My daughter keeps getting rashes… I don’t know what to do 😭

Ever since my daughter was about 3 months she started getting rashes in her diaper area. I have tried switching diaper brands several times and I used to only use unscented wipes for sensitive skin but now I make my own homemade wipes which seem to be helpful. I don’t know what is causing her to have diaper rashes all the time. I could never get rid of it. I have 3 daughters and this has never happened until now. She is 10 months now and I don’t know what to do. I literally never let her sit in soiled diapers. As soon as she pees and poops I change her. The only time it really “sits” is when I am driving for a while which could only be like 30 mins and even then she will develop a rash in that short time after it has gotten better. The doctor gets on my nerves because he assumes I let her sit in it all day but that’s not the case here, I promise. He says it’s not yeast infection. He prescribes me with a cream that seems to be helpful and has been using it since she was 3 months but I am wondering what the cause is so that things can improve and she won’t be dependent on that prescription cream. I can’t wait to potty train 😭 Any thoughts?

Update: She is breastfed and I watch what I eat. I also pay close attention to what baby foods she eats as well.