I've had shingles and my doctor gave me 40 mg. daily of prednisone along with Valtrex. I've only been taking the prednisone for 2 1/2 days and I've got an awful headache. Since I've only been taking it a short time do I have to taper off? I've been taking the Valtrex for five days so I don't think it's the Valtrex giving me the headache.