While it's not possible to establish a diagnosis without a doctor
's visit, there are a few things that come to mind. You should take these into consideration when talking to your doctors
">primary care doctor.
Many things can cause you to be sleepy and have a lack of energy. Many of the most common of these things you have described already - hypothyroidism, depression, poor sleep hygiene, stress, and anemia. Another very common reason for being sleepy is sleep that is disrupted by blockages in your airway while you sleep, called Obstructive Sleep Apnea. Things like being overweight and snoring loudly can suggest this diagnosis, but it can be found even in people without these risk factors. To diagnose obstructive sleep apnea requires a sleep study, where you sleep in the hospital and are observed overnight.
Another possibility is that you have an infection that is making you tired. Infectious mononucleosis, a disease caused by the Epstein-Barr Virus and referred to commonly as "mono", or many other viral infections can be associated with fatigue after infection which may last for months. There are blood tests that can suggest this diagnosis in the appropriate patient.
Finally, there is a syndrome of unclear cause called Chronic Fatigue Syndrome, a disease of excessive fatigue which is typically diagnosed only after other causes of excessive sleepiness are ruled-out. There are doctors who specialize in the treatment of this syndrome, using techniques like cognitive-behavioral therapy.
I hope you find these suggestions useful. Again, it is not possible to establish a diagnosis without seeing you in person, but it sounds as though you have had a reasonable workup for many of the common causes of excessive fatigue. You should talk to your primary care doctor about these possibilities, to determine what further diagnostic steps might be useful and what therapies could be tried.