Hi Fever with headache and generalized weakness is a sign of viral infection. The appearance of the blisters indicated a viral pathology to it Treatment basically includes pain relievers, anti pyretics and a short course of anti viral drugs and nutritional supplements depending upon the nature of the disease. The cause needs to be investigated with blood work up. Please visit a General Medicine doctor or you can consult me directly via practo for further evaluation and management. In case of further doubts, please feel free to write back to me. Regards Dr Prashik Meshram