Make doctors appointment for 'under-active thyroid' they will take a blood test and get back to you.
I suffer from it and so does my dad, you feel extremely drained/tired, yawning often, lack of energy and difficult to 'get going'? Even when you had decent sleep and good diet. It's a lack of thyroxine hormone being produced from your thyroid gland in your neck but is also controlled by the brain.
My last job as a web designer was doing 12 hour days, getting up at 6am to commute and not home until gone 9pm sometimes. At the time my daughter had just been born so sleep was very little. Always nodding off and micro sleeping, sometimes standing up waiting for train.
Anyways just get tested to be sure, can get really bad if not dealt with.