Itchy armpits?

This sounds so gross but I wonder if any of you have any experience with this... for the past few months my armpits have been itching excessively. To the point that it HURTS. I have changed out soap, deodorants, foods, etc. I shower often, I’m a clean person. I still have no idea what it is. I will go to a doctor, but it’s turned into a dry rash and discoloration and I wanted to check with others before my appointment. Any ideas??