What Does Pain In The Thigh And Hip Along With Chills And Fever Indicate?

Since September of last year, I have had 5 times, recently another started yesterday, I get pain in the right thigh to hip area... shortly after that I start to get the chills which last approx 2 hours with a fever up to 104. I then get a large red mark on the right thigh, its as big as my hand. The mark on the thigh is warm/hot to touch but disappears after approx 3 to 4 days. I have seen 2 different doctors that haven t figured out what is causing this. Do you have any suggestions? All they tell me is it is a virus, but with getting this in September, November, December, January and again in May... what kind of a virus would this be and with the red mark in the same spot and each time just as big.