by noon I start feeling weak , tired and eyes are very tired

I am a 55 years of female with pretty good health. Other than sleep apnea for what I use a CPAP every night and take nuvigil 250 mg. a day.
I have been feeling sick lately for the last year but it is getting worse. I can sleep all night with the CPAP and get up in the morning and by noon I start feeling weak , tired and my eyes are very tired. So I f=have to go and laid down. Once I sleep 30 minutes to 1 hr. I get up and feel okay. But when I get weak I feel that if I do not go to bed I am going to pass out and fall.
My doctors order a lot of test which came back normal, my CT of the brain and all the cardiac and neurological testing came back normal, but I still feel sick.
Is there anything you can advise me on. I am just getting very concern because I feel this situation is affecting my life.
I feel I can not work outside the home because what will happen when I feel like this and need to go to bed?
I really want to feel better and feel productive. Please help me.
Thanks,
Yolanda