I have fatigue, muscle aches & occasional sharp pains in my mid low right back. Recent bloodwork shows low levels of co2. Doc has no idea why. Help?

Adrenal fatigue. Find a functional medicine doctor in your area to help explore your adrenal function with a 4 point cortisol test as well as thyroid function. Cortisol is your energy currency but also an anitinflammatory (think manmade prednisone) so low levels cause fatigue and low back pain and poor thyroid function can cause muscle aches as thyroid is involved with muscle relaxation. Co2 is inconsequential.