Hi,
Various disorders can cause fatigue, diabetes, thyroid to apnea. As other member suggested, have pcp do a blood lab work up and refer you to a sleep study, if all your labs return normal.
Good luck !
A suggestion: See your primary care physician and see if a sleep study might be appropriate. A study can determine is you have any sleep disorders that can be interfering with nightly sleep. Also your physician can make decisions if any other tests may be appropriate to determine is any other health issue may be causing your "out of it" problems.
Good luck!