Your symptoms are fatigue, but very much pronounced. After reading your story, several things came to mind: sinus & ear congestion; general fatigue; adverse effects of a medication, food or substance; or atypical migraine. To diagnose this over the internet is virtually impossible, but I would suggest the following:
1. Keep a journal of your sleep. Ensure that your are getting 8 hours of sleep. Note naps, etc
2. In the log, write down the times when you feel the thickness the most and what other symptoms you are feeling as well.
3. If you smoke or use tobacco products, stop them
4. If you take energy drink stop those
5. If you drink alcohol, stop that
6. After the above steps, if you still feel these symptoms after 2-3 weeks, go to your primary care provider and show him the log.
Just to make things clear....
I sleep well actually... the only part of the day i enjoy. I dont smoke. Been sober for 2 months. And i dont drink coffee, energy drinks. I am now going to give myself as much rest as possible.