I had the same issue for more than half my life and doctors told me nothing was wrong,well I proved them wrong so don't let them tell you aren't sick! Remember The wearer best knows where the shoe pinches.
Let's go back over the following
The basics
Amino and Vitamins - Take a good multiamino and multivitamin, some disorders respond to vitamin and aminos, take with food.
Exercise - Do you exercise, what happens when you do?
Health - How is your general health, lungs, weight, heart etc?
Habits - Do you drink or smoke much?
Sleep -
Do you wake in the morning tired?
Do naps feel like they refresh you?
How fast can you fall asleep?
Do you suddenly fall asleep like out cold or just nod in and out?
Do you make noises as you sleep or move about?
Do you sleep soundly or wake up?
Do you ever wake and can't move?
Do you get irritated a lot, impatient with people?
Doctor Tests
Blood Tests - Full panels
Head injury - Have you had any head injury in the past? Head injury can cause symptoms years later.
Epilepsy - Epilepsy can cause tiredness without obvious seizure
MRIs - To rule out structural damage or abnormalities
Psychology - To rule out depression/anxiety/stress (Sounds silly but it can unconscious)
Neurology - To rule out neurological causes
Dentist - Yes the dentist, the dentist can be helpful to see if you grind your teeth at night.
Sleep Disorder - An overnight sleep study with MSLT will rule out most sleep disorders.
Unusual Disorders
Idiopathic Hypersomnia (IH)
A very rare disorder, this is what I have, you can read my post about it.
http://www.longecity...ycythin-review/
https://en.wikipedia...hic_hypersomnia
Treatment: Clarmycythin, Flumazenil
Clarmycythin takes about half an hour to fully kick, so take it when you are usually tired, for me it was always! So I took it in the morning and it gave me 3 hours of wakefullness. If it manages to work for you I can show how I dosed it to get a permanent fix.
Lyme Disease
Can cause a persistant tiredness even after it has been treated
https://en.wikipedia...ki/Lyme_disease
Treatment for regular: Antibiotics
Treatment for persistant: lyme Low dose naltrexone, B cell suppression
Food Intolerance
Intollerance is different from allergy, intollerance usually causes digestion issues and tiredness
You can run a big skin allergy panel but it isn't entirely accurate.
Treatment: Altered diet such as Ketogenic, Vegetarian or paleo diet for example
Auto Immune Disorder
There are many of these, a standard blood assay rules out some of them, requires immunologist
https://en.wikipedia...oimmune_disease
Treatment: Depends on the disorder