headaches, tmj, migranes, constant, daily

I've been getting constant headaches for about 2 years now and i've seen various doctors and have had various tests run/treatments but all to no avail. Last month my dentist said i had TMJ which would explain my headaches however i would have thought with TMJ i would be getting jaw pain and difficulty eating? I have not experienced this. Also, accompanying my headaches is usually nausea, dizziness, generally feeling of fatigue, and i find it hard to balance sometimes. My headaches appear dull and tight, usually around my eyes and forehead, as well as the back of my head and neck being tender. It is so bad that i cannot sleep as my head is consumed with pressure and i have to keep tossing and turning to get into a good enough position where the pain is minimal but it rarely happens. I'm wearing a nightguard on my bottom teeth as prescribed by my dentist however i am seeing no improvement and i'm thinking the headaches have another underlying cause?
Please help me, i am only 17 and i feel like the last two years have been robbed from me, the extra stress is making me ill and my appearance is gaunt and my digestive system is up the creak.

thank you.