I'm 19 years old and I have back pain for over 3 years now. It started due to posture, in my whole back. A little less than 1 year from now the pain focused in my lower back, getting weekly worse. I did 50 sessions of Global Postural Reeducation (RPG) and the pain was no better, even though my posture was almost 100% in what we call "normal". My physician told me I should go to see a rheumatologist, so I went. She barely looked at me and said I have fibromyalgia. My psychiatrist and my psychologist (I have depression) said it could be a possible diagnosis, so we tried two different medications. Some months passed, the pain was getting worse.
- In the past 4 months I have developed the following symptoms: Extreme fatigue, tripping and falling all the time, muscle weakness (mostly in right side of body). One day I noticed I have a huge difficult to hold small objects with my right hand, like buttoning a shirt, and everything I hold just fall if is not entangled in my fingers. Lifting a pen feels like I'm trying to lift a car. My right foot drops sometimes when I'm walking which caused me to fall several times. I had fasciculation in the left muscle of the inside part of my wrist for two weeks and some days my hands (the right is always worse) shake badly.
Since I can't stand still without falling and I walk like I'm drunk and I fall, I'm now using a cane to help me to walk and climb stairs (both my legs hurt badly while trying to climb or go down a stair). In the last 1 month I had to go to the ER twice (in the same week) due to awful lower back pain that paralyzed the right side of my body one day and in the other along with the pain I was feeling eletric impulses like a shock going up and down my back and it did hurt a lot. I have now writing issues, is hard to hold a pen and I often misplace letters - including when typing - and my handwriting looks strange. I also am having a hard time concentrating in anything I do and my memory is bad enough that I had to stop three times to remember what I'm writing here. In a conversation my speech is like Ï went to the market yesterday to buy... hm... An... Apple is the name? No, not an apple. Wait" and this go like that. It seems worse when I'm tired or when my lower back hurts more than the usual daily pain. I have myopia (since 6 years old) and astigmatism (since 14 years) and it's been a while since I went to the ophthalmologist, so I can't say if these are symptoms, but lately my vision is more without focus, specially in the corners and its like I'm seeing double edges in everything. I also noticed I have to blink more than usual to see like I used too, and my eyes move too fast which makes me dizzy sometimes.
About exams:
Full blood test including B12 deficiency, inflammations, even a HLA-B27 test, all came back normal and negative for B27 protein.
Did EMG of upper arms, normal (I don't know if this is true but I read in some articles that the EMG is better done when you know what you're looking for because the position of the needles can change to do the test depending on what could be the diagnosis);
Brain CT came back normal, but I can see small white spots in many places - I can upload some photos if someone wants to see)
Brain and cervical MRI with and without contrast, normal too but I can see white spots in all of them too.
Lumbar MRI showed degeneration on L5-S1, something like a herniated disc, fluid in one of the discs. I don't have the common symptoms of herniated disc, though.
I'm wondering about asking my neuro a spinal tab and evoked potential test to rule out or help confirm the diagnosis of MS. Is this the right next step or am I missing tests I should ask too? If not MS, what else could I have and what should I do? My lumbar problem could be a part of MS? I'm young and I feel like I'm losing mental health and my life trying to find out what is wrong and is disabling me more and more...

Thanks for any answers and for the help!