Brain fog. Ear ache. Tooth ache. Pressure on one side of head. What could this be? A

Ear issue?? It sounds like you could be a ear issue but x-rays need to be taken to rule out wisdom teeth issues.
See a doctor. Could be tooth, or sinus infection, or many other dangerous and not dangerous things. Go see a doctor and get examined.
Too many. Too many possibilities to be answered here. You require 2 concurrent examinations. See your Dentist to evaluate for tooth, sinus, gum, TMJ, etc. See your Physician to evaluate for Ear, sinus, neurologic, systemic, etc. Treatment or referrals may be indicated. Can't fix you over the computer. Not a DIY project. Please seek professional hands-on care.
Many things. A examination by a doctor will be needed. There are many causes of your symptoms.