To be honest i think you might be misunderstanding the MS related symptom description and patterns, its common issue when your struggling to find the medical condition that makes the most sense of what you've been dealing with. Unfortunately because MS has a lot of similar/same symptoms as lots of other conditions, typically much more common ones too, being in medical limbo can get very confusing as well as emotionally draining.
For the record, a mental health condition doesn't exclude anyone of having other medical conditions, and there wouldnt be many chronic medical conditions that dont have anxiety and depression on their symptom lists so if the condition its self didnt directly cause a mental health issue it could of indirectly caused a mental health issue. Mental health and chronic conditions can often be a what came first chicken or egg senario, if that makes sense...
"electric shock-like sensation in my neck when bending it a certain way" is suggestive of a structural spinal issue temporarily pinching the peripheral nerves, neck flexing forward is becoming more common with the amout of phone and tablet usage these days, its creating an extended bend in cervical spine (neck) its possible there is a structural issue but keep in mind the evoked potential test is looking for perminent damage to the peripheral nervous system and medical conditions like type 2 diabetes dont show up in blood tests and nerve tests until its been around for awhile. I have 2 family members that where obviously diabetic but tests were normal for years before they were diagnosed, stupid really to not be diagnosed even though they both were obviously symptomatic long before the tests agreed with their reality, just saying normal test results dont always make things clearer.
"often my sight will go "black" for a short amount of time, not only when standing up.
I have not yet had very extreme symptoms in my eyes, but in the past I have experienced my vision becoming blurrier, as if I need glasses, but the eye doctor could not find anything wrong with them.
Additionally I frequently experience double vision, where it feels like it is impossible to focus my eyes on something......To get some of the more specific symptoms, I'm very sure that I have heat intolerance, since heat makes me extremely fatigued and feel like I need to faint. (For example, I once put my hand that had been under hot water on my forehead and almost passed out.)"
With a neurological condition like MS, heat intolerance means the return of the MSers preexisting MS symptoms and or the worsening of MS symptoms with an increase of the bodies core temperature eg unilateral Optic Neuritis (ON) is a very common MS visual symptom that causes the vision in the nerve damaged optic nerve to black out for a time frame but you can also experience an irregular shaped ovalish grey semi see through blob um like looking through a smeared blob in the way of what your looking at .
So an MSer with ON if exposed to heat long enough to raise their core temperature, eg hot days, kitchens, showers, baths, hot tubs etc (actually the hot bath test use to be how they diagnosed MS) will typically experience heat intolerance and the one eye with ON will temperarily black out etc again, fatigue is common too but once the MSer has cooled down and rested long enough they return to their individual normal self.
What you've described experiencing that your thinking is the same as MS heat intolerance sounds more consistent with heat exhaustion and those types of temperary visual issuse sounds more consistent with a focusing / eye strain problems that honestly could be related to migraines, sleep deprivation, diet ie iron deficiency
Dont forget that even when the description doesnt really fit with whats normal when a symptom is MS, it doesnt mean the symptom is caused by a mental health issue, it could easily be a misinterpretation of symptoms associate with a medical condition that you are already diagnosed with and treated for or symptoms associated with a medical condition that you are yet to be diagnosed with.
Perfect example i have is whooping cough; DD when a young adult got really sick, difficulty breathing, dizzy, fatigue, nausea but she does have a diagnosis of anxiety so when GP did blood tests and found nothing DD was told it was anxiety...she got worse to the point of returning about twice a week for ages with same tests done all normal so no help. Getting desperate she asked to see another GP or get her file so she could find someone who'd actually help her. Different GP same clinic did an air way test and she was complaining she was struggling to breath, she had 3o% lung capacity and sent for different tests which found the whooping cough and she'd been out in the community highly infectous and not tested because its a childhood condition and she was a young adult. Moral of the story, normal test results doesnt mean normal if your dr didnt test you for the medical condition you actually do have...
Personally i'd stop talking to your GP about MS and ask your GP for a referal to get the possibility of a mental health cause ruled in or out but what else could this be that i havent been tested for? Showing you are open minded to what ever the cause may be can often make a dr more comfortable double checking a few other things, even checking medication side effects.
Hope that helps........JJ
I also have, as far as I remember always had a horrible sense of balance.
Since I don't know how to edit my question, I would also like to add here that occasionally I experience a electric shock-like sensation in my neck when bending it a certain way.