No, I haven't used anything different and I am on such a low dose so I don't know what to do.
It sounds like you have developed an allergy to it. I would call your doctor.
The two may not be connected it may be a allergy rash, have you used anything new recently, shower gel , shampoo, laundry detergent any new materials in underwear?
it is due to the fact that your body has developed allergic reactions to the narcotic drugs that you are taking. Its better to consult a doctor for better solution of the problem.