I know what your going through. That spacey/lightheaded feeling?? I've had that for the past 2.5+ years. For me it started in a similar way - i was at school, and a few days (each with about a week or more gap between) i would get this feeling while in the school hall during assembly. Ofcourse because of this i needed to leave the room. Then one of the times it happened, it didnt go away when i returned to normal school classes. After this, i went home from school and missed the last couple of days of term and this event brought on anxiety. I avoided public situations, and when i was about to go back to school started having panic attacks. Everyone always puts it down to anxiety, but i know the lightheaded/spacey feeling came before the anxiety. The spacey feeling caused the anxiety. I have done alot of research trying to find my answer. Here are some of the possibilities- TMJ, BBPV, inner ear disorder, candida, EBV, lyme disease, poor circulation, dehydration. There are many different viruses or parasites which can cause it, or it could simply be your eyes or allergies to a food or something else. I am trying to eliminate stuff by changing my lifestyle habits. I'd suggest you see an naturopath, or see if acupuncture or a chiropractor can help (it has for many others :) )
Also, you said you clenched your jaw randomly - look into TMJ.
The headaches - they could be causing the feelings. Get this checked out :)
Keep us upto date with your recovery especially if you find your cure :)
I am going for a CT scan this Saturday.
He also suggested it may be due to the birth control medication I am on. I am yet to stop using it as he wants me to keep using it until after the CT scan is complete.
Will update soon.