OK, so you've been told by a neurologist, your primary care physician and a psychiatrist that multiple assessments using medical and psychological methods to assess brain injury have failed to bring up any evidence of brain injury. Is that right?
I'd never suggest that anyone blindly listen to a medical opinion, but it seems that you're convinced that you have something that no one can find any evidence of, and despite the fact that you have no medical or psychiatric experience, you believe that you can provide a more cogent diagnosis than people that have received 10+ years of training in their fields of expertise.
You do realize that this is the very definition of anxiety and being a hypochondriac, yes?
Unless you breathed in nitrous oxide until you lost consciousness, and your friends continued to administer ONLY nitrous oxide for 3-5 minutes after you lost consciousness, you will not have suffered a brain injury.
Self-diagnosis is NEVER a good idea. You're in a high stress environment, and you're a depressed anxiety sufferer, yet you find it difficult to believe that anxiety, coupled with an unhealthy lifestyle, could have effects on your vision, blood pressure, balance and memory?
Zoloft might be a good start, but you might think about learning how to deal with the root causes of the anxiety. I'm an advocate of Cognitive Behavioral Therapy, which I would suggest to anyone with anxiety, but medication and psychotherapy can also be highly beneficial. Medication alone may not do much more than mask your issues. Many doctors will prescribe medication to help you manage symptoms, but this doesn't actually TREAT the symptoms in most cases.
Go back to your doctor and ask for a referral to an anxiety specialist. It could change your life for the better.
I have seen a neurologist and gotten an MRI and a few blood tests that "seem fine" but have read that most tests wouldnt pick up mild brain injuries. I have seen a psychiatrist and have been taking 50mg of Zoloft for about a month and a half. They say im just stressing/depressive. no one believes me. I have been anxious my whole life but this is different. Trying to decide if i should go back to the doctor or wait it out longer. Im just hoping to move past this.
It is unlikely that the nitrous oxide is the cause of your problems, i think it may have triggered anxiety by bringing on strange sensations. After all, if N20 was that dangerous it wouldnt be given to labouring women :) xx
Perhaps you are more susceptible to the influence of the nitrous oxide, and perhaps other drugs as well. The brain is pretty sturdy. It sounds like anxiety is the cause of your symptoms. Give yourself a break. Relax and listen to some music. Go dancing or running. Forget about it and see if it goes away. I am a subarachnoid hematoma survivor and doing much better with time! Brain injury is relative.