Have you had blood tests recently? It might be worth checking B12, folate, Iron & vitamin D. Low of any of those can cause tiredness.
Be aware that any B12 in the 4-6 months (supplements, energy drinks, etc) will cause a false high result and doesn't mean it isn't the cause! Low folate can also cause a falsely normal B12 result.
Make sure you don't take any iron supplements in the 5 days before the test either!
I'm happy to try and help you interpret results. I was unwell for years, getting more and more exhausted all the time. At my worst I was waking/sleeping the following:
Waking around 7am.
Fall asleep at my dear around 10.30am at work for around an hour on and off.
Go for an hours sleep around midday.
Fall asleep at my desk around 2.30pm
Sleep in the car as a passenger on my way home at 5pm.
Go straight to bed when I got home around 5.30/6pm where I'd stay til the morning.
I had no energy to eat a meal, never mind cook one.
At a weekend I'd sleep til 2-3pm.
Obviously it built up to this, it wasn't instantly like it! When I read about B12 deficiency it was like a lightbulb. My level looked low normal but my doctor agreed to trial it. Monthly injections made a small difference. I then bought my own to self inject - I saw my doctor after 3 weeks of every other day injections and she couldn't believe the difference and instantly prescribed it to continue at that rate. It gave me my life back,