head pressure

I have had a problem with feeling a pressure in my head for
many years. I currently take medication for depression-
Effexor and Wellbutrin, but this problem occurred before my
being medicated. I feel a strange pressure on my forehead,
accompanied by a feeling of spaciness and inability to think
clearly. It is somewhat hard to describe, as it is not
painful in the conventional sense, but it is extremely
uncomfortable. I also feel an overwhelming need to lay down
and sleep. After a nap, the symptoms usually go away. This
condition has been incredibly problematic, in school and in
the workplace because I am unable to function normally. My
head feels numb, I cannot focus on anything, but a desire to
get rid of the feeling. Could this be allergies, sinus,
blood pressure, brain tumor? I am at a loss. Diana