Skin fungal infection

I don't want to gross anyone one out but I need some help. I have a rash on both of my underarms. The doctor says it is a fungal infection. I thought it was going away but it keeps coming back. I have been on a prescription cream for two weeks. It was almost gone and it came back again. I am eating lots of yogurt and have put plain yogurt on my underarms. I have also put vinegar on the rash.

I think the prescription cream is just keeping the area moist. There is a thick "scab" on one of my underarms. So I sort of feel like the medicine is not getting to the skin.
I usually use a powder that is has a base of corn starch. I just thought that maybe corn starch isn't that good when dealing with a fungal infection. So for the last few days I've stopped using the corn starch.

I don't know if I should use my deoderant before I apply anything or after.

Any advice would be appreciated.

Thanks, Loretta