Too Tired

I have been too tired lately. It's an ongoing, chronic problem lately. Driving is becoming a hazard. I get enough sleep, I'm even using my CPAP every night. But I still can't shake the tiredness that comes over me. My knees hurt. I'm sure that losing weight will fix them, but I can't seem to make the weight loss continue, no last. I keep thinking it's going to be different, but yet it never is.