I have had an ongoing headache on right side of head for four days now. Any ideas? Doc has me on fierocet, xanaflex, and amitriptyline.

Second opinion? Headaches can be caused by a number of possibilities. These include hormonal fluctuations, dehydration, muscle tension, sinus/allergy issues, infections, migraines, tumors, and a number of other medical issues. If not improving, it may be time for a second opinion, or time to seek the help of a neurologist.
Have you seen. A neurologist? Were you on these meds before the headache? In what order were they added? No easy answer, but would get back to your doc soon.