What Causes Lack Of Sleep And Constant Tiredness?

Yes, I am almost 73 and was told I have fibromyalgia many years ago. I am so tired and feel so run down all the time. I never sleep well so wake up like I never went to bed. I just feel that I have something else and wish I knew how to find out. My D level seems to always be low, but other than that, fairly normal blood tests. Sometimes I just wonder if I am allergic to something or some food. I just wish that my remaining years could be ones that make me feel better. Anything that I should be tested for?