looking for the cause and a potential treatment for excessive daytime sleepiness / chronic fatigue

Hello,

I am currently looking for the cause and a potential treatment for excessive daytime sleepiness/chronic fatigue/exhaustion (not a CFS diagnosis) which I've been struggling with for a decade now. I feel tired even though I sleep enough, lack energy during the day, have memory issues and generally feel cognitively impaired. Drastically different from what I felt like years ago.

I am in my 20s and also an epilepsy patient. However, the anti-epileptic drugs are not the cause of my fatigue symptoms, but have proven to be very effective against my epilepsy and I haven't had a seizure since taking them.

I've had two sleep studies and it was concluded that I do not suffer from Sleep apnea, Restless legs syndrome or Narcolepsy. I do not have any trouble falling or staying asleep either. The only thing that wasn't right according to my doctors is my sleep architecture itself:

I can only paraphrase what they said as I dont have the sleep study report at hand right now, but could get it to provide further details if necessary.

Both sleep studies showed that the individual phases of my sleep are "delayed" and that the proportion of REM-Sleep I get is shortened. According to the doctors, there is nothing that can be done about that as treatment usually targets the causes for structural issues in sleep but not the sleep architecture itself (i.e. sleep apnea can cause disturbed sleep architecture, so you treat the apnea and only thereby alter the sleep architecture).

Given the severe impact my symptoms have on my life, it is hard for me to simply accept a "We don't know why and we can't do anything about it". Hence I am asking/looking for additional information about disturbed sleep architecture which is not caused by the usual sleep disorders (as mentioned above: RLS, Apneas, Narcolepsy), other potential causes and most of all treatment possibilities.

I have, of course, already looked into other causes for my fatigue, had my thyroid checked, brain scan done, psychological evaluation and other things. Thus far the sleep architecture is the only thing that is out of the ordinary.

Thank you for taking the time to read my post.