What Causes Extreme Fatigue And Weakness?

I have had extreme fatigue and extremety weakness for 2 weeks. I had had some drainage and coughing. 50 year old heathy male otherwise. Normally exercise but haven t felt like it. Been sleepin well and no fever, chills. Blood pressure is good and A1 C is borderline for several years. Been worried... Have 3 young kids. Thanks Mark