Rash On Tongue, Itchy, Thirsty, Dry Mouth. Tried Medicines, No Help. Solution?

Hello I have been getting this red rash on my tongue in and off for awhile now it can last anywhere from a few days to a few weeks. It consist of little white and red spots around mostly the side and tip of my tongue also my tongue becomes itchy and the tip and sides of my tongue also turn strawberry red. When this rash does appear I become more thirsty and get a dry mouth quickly. I seen my family doctor a number of time and he has given me a few different types of medication but none of them have worked for me so far. When I use mouthwash it burns my tongue a lot and it becomes very painful for awhile but after about 30 mins I get a few hours of relief from my tongue. Also I am a 24 year old male if that helps