Could Excessive Sleepiness And Fatigue Indicate Thyroid Problem?

I recently went to the doctor and he felt my neck & asked several questions, stating my thyroid was enlarged. I did bloodwork, but the results have not come back yet. He mentioned getting an ultrasound done on my thyroid. I am also very sluggish during the day, I could fall asleep at any given minute of the day and have trouble functioning at all because I am so sleepy. I have absolutely no energy to do anything and have to force myself to even do simple things, like cook supper or fix my hair in the mornings. It doesn t matter what time of day it is, I am always sleepy and tired. If my thyroid is off, would this explain my lack of energy? I have a hard time getting up in the mornings, and I even have a desk job, so its not like I have to be physically demanding at my employer. But even with the desk job, some days are just so hard to function because I am so sleepy. I was able to get a prescription from my doctor for phentermine (I told her I needed to lose weight), but really I just wanted it to help wake me up in the mornings and be able to function normally. I ve lost about 15 pounds on it, but that s the main reason I take it - to simply be able to function. When I don t take it and I m at work, my eyes will get glassy and start rolling around and I could literally lay my head down and fall asleep right at my desk. Its awful. I ve asked the doctor about it, but she blows me off saying I just need to exercise. I seriously thing something else is wrong. All my bloodwork is normal every year. Even my thyroid bloodwork was normal this time last year, but I saw a new doctor this week and he s the one who tells me something is wrong with my thyroid. Could this be the cause of all my sleepiness, sluggish behavior, etc.?