A sleep study may help as I used to have strange problems when my Central Sleep Apnea was a problem. I first became aware of my CSA during an EEG with a sleep session when my breathing stopped.

Here is a wearable monitor that reports to a smartphone that may give you some ideas if O2 levels are involved.
http://www.amazon.com/Withings-WAM01...pulse+oximeter

If you suffer a oxygen deprived sleep, the next day would be miserable, at least it was for me.

EEG's are not conclusive. They only tell you that you did not have a problem during the EEG.

Some have had 24 hour and longer EEGs.

Have you had an assessment by a behavioral optometrist ? https://nora.cc/ has referrals. Convergence and other eye dysfunctions can cause a myriad of issues.