What Causes Persistent Fatigue And Tingling Sensation In Toes And Fingers?

I have been suffering ongoing fatigue for about 6 years. In addition, my fingers and toes tingle and burn, I have irregular bowel concerns including varying constipation and diarhhea, joint and muscle pain, night sweats, and skin rashes on my extremities. I am a 73 year old female who has had a past history of good health. I am not a smoker or a drinker of acohol. Six weeks a,go I was diagnosed with ishemic optic neuropathy. All the test for Giant Cell Arteritis have been done and are negative. Also, I have had the carotoid arteries tested, and an echocardiogram and they show nothing negative. I feel that there is something going on within my body, but can not get a diagnosis.