What you are describing happens to me too, but I don't actually vomit, I just suddenly feel like I am about to vomit, but I never have. The pressure on eyes, and the imbalance are exactly the same for me. Also, each concussion gives me slightly different symptoms. Nausea did not come until my 5th concussion.
So either we are both weird, or we are in good company.
Fell off a horse in late winter of 2009 blacked out for a couple seconds, had amnesia for 10 hours (still don't remember this time), had 2 CT scans, 2 MRI's, 1 MRA all negative. Since the first concussion I have continually knocked my head into different things purely by accident or from being stupid. These many concussions over a short period of time have caused
constant migraines, nausea, and dizziness/lack of balance.
Migraine triggers are:
light sensitivity (especially to florescent or bright lights)
sound sensitivity (especially to high pitched or loud sounds)
temperature sensitivity (especially to cold or extreme heat)
activity (especially if breathing increases or head is jostled)
pressure on head (sinuses, hats, headbands, sunglasses, pony-tails)
lacks or quality (food, sleep, water)
tension (stress, tight muscles, tired eyes, sickness)