My Husband Is 53 Years Old And Is Suffering From

My husband is 53 years old and is suffering from muscle pain in the upper body and has a low grade fever of 99.8. He also has muscle pain in the right thigh on the back of the leg. This has happened before and gets better then comes back even worse. He has been tested for lupus, ra , gout. The only thing that comes back positive is a "psuedo" gout. He is very healthy otherwise and rarely complains, but has been knocked out by this several times already this year. He is flat on his back in bed right now which is extremely unusual for him. Thoughts??