My 9 month old boy has a terrible rash and I dont know what to do anymore =/?

My son has had this rash for about 2 weeks now. I went to the doc after about 2-3 days of this rash after I had used ointments and corn starch and all of the above. Of course the morning of the appt his area looks 110% better still red but way better he says to not use wipes and to just run cold water over it so I dont irritate and it wont come back. Well it came back and with avengance!! Also with bad poop spurts about 5-7 times a day half are diarrhea. So I took him back immediately and the doc gave me some Nystatin and Triamcinolone Acetonide and told me to cont with the cold water cleanings and to give him pedialite. Well it has been 3 days and it still looks the same just no more swelling and still has 5-7 Bm's in a day. Should I ask for a different doc or diff medicine? I just feel so bad and need some thoughts and please keep all negative thoughts to yourself. Thanks in advanced!!