What Causes Stabbing Pain Along With Burning Sensation In Feet?

I have plantar facitis but also experience the following burning stabbing stinging pain in both feet also at times the bottom of my feet will turn bright red as if they are sunburned and are almost impossi bly painful to walk on I have been tested for diabetes and am neg for ..I also suffer from aldultonset stills disease and fibromyalgia I have the boots for plantar facitis butsofar nothing has worked the stinging and fever like in my feet is very worrisome any ideas?