What Causes Soreness In The Neck And Fatigue Along With Depression?

I feel feverish, but my face is cool when I touch it. My temperature is normal. My neck muscles feel sore and achey. A little fatigued physically. Malaise. Mild depression. Did my usual challenging workout this morning, but felt weak and strangely uncoordinated. Aches and pain in my feet, knees, hands too. Difficulty concentrating at work. I m 60 years old, but fit and have been very active for 40 years. Weight lifting, cycling, running, aerobics, yoga...started doing HIIT in the last year which has begun to feel rather brutal.