20 year old male sick to stomach pressure in head losing train of thought?

Central process? Although your symptoms may represent an atypical migraine, greater concerns may include: meningitis, concussion/brain contusion/subdural hematoma from closed head injury, atypical seizure. Although there is a substantial GI component to your distress (possibly secondary to altered vagal tone or involvement of the "emesis center" of the brain) please seek immediate neurologic evaluation--go to er.