I had similar symptoms and after a blood test it was confirmed that I have Hashimoto’s/Hypothyroidism. I was falling asleep right after I ate, which I never did before. Have your doctor test your TSH levels, T3-free levels, T4-free levels, and your thyroid antibodies. I do take medication daily and for the rest of my life for it, but small price to pay to stay awake! Good luck on your health journey.