Hello, You are suffering from butt rash that is causing you discomfort due to peeling, soreness and pain. You are also having stomach upset, diarrhea, fever and nausea. You are suggested to maintain hygiene. Take bath regularly and use antibacterial soap or lotion. Avoid use of harsh soap or chemical based body lotions. You can apply ointment clotrimazole on the area affected as it can be caused by fungal infection as that area often remains moist and warm. Using a humidifier can help hydrate your skin. You can also use water based moisturizers daily. However, rash associated with fever, stomach upset and nausea can be indicative of shingles. To get relieve from discomfort you are suggested to take oatmeal bath, cold compress on the area, applying calamine lotion and taking acetaminophen, one SOS when fever, pain and discomfort is helpful. Get clinically examined by a health care provider or GP, get STD tests done to detect STIs or shingles. If reports are positive you will be treated with antibiotics / antivirals. After gym, make sure you take a bath, Avoid rubbing too vigorously or scrubbing in the shower, use soft toilet paper, wear loose cotton underwear. Take antidiarrheal to stop loose stool. Take semi solid diet for a few days. Stay away from addictions if any. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician