Some thoughts based on the information you provided:
A sleep study would be appropriate based on your unrefreshed sleep, fatigue, twitching, pain, brain fog and migraines. A sleep disorder can cause many symptoms and should be ruled out.
Since you have back pain it would be a good idea to rule out mechanical back problems (bulging/herniated discs, stenosis, ect.). Pain in legs, arms, sciatica, back/neck pain can be caused by mechanical back problems.
Your blurred vision appears to be associated with your headaches/migraines, this can be very typical for migraines. Visual disturbances (auras) can happen with and without the actual headache/migraine.
This will give you more information:
Anxiety can cause heart palpitations, heart racing, lightheadedness, chest pains, insomnia/sleep difficulties, abdominal pain, constipation/diarrhea. If your symptoms go away once your anxiety is treated it's a good bet that those symptoms were based within the anxiety.
As far as Multiple Sclerosis --- MS has a diagnostic criteria, The revised McDonald Criteria.
At this point the only test you have had that might point to MS would be the brain MRI but it appears the findings indicate migraines as the cause and not demyelination. Multiple Sclerosis is a disease of the Central Nervous System(CNS) this includes the brain, spinal cord and optic nerves, and is a demyelinating disease.
I can't tell you if you have MS or not, that would be up to a Neurologist after testing and exam. I would certainly consider the sleep study, anxiety treatment and mechanical back problems.
Best wishes on your diagnostic journey.
Thank you for your feedback. I actually did see a sleep specialist one month ago; unfortunately, I did not like him and the appointment was not of any help. He seemed to think that my problem was delayed-phase sleep disorder, which I do agree with; however, he did not suggest doing a sleep study because I'm not sleeping (and you have to be able to sleep during the study). Anyway, I still wonder if I might have sleep apnea or some other sleep disorder that I'm unaware of. I know that mechanical back problems could be causing some of my symptoms, but I would be surprised if I had a herniated disk or spinal stenosis (I'm 24). However, it's not impossible. Anxiety can definitely cause many physical symptoms, but I don't think that all of my symptoms are due to anxiety. I might have some underlying anxiety that I'm not completely aware of, but I do think there is something else going on. Although the neurologist did diagnose me with migraines, the radiologist's report of my MRI did say this: "Minimal white matter signal changes as above, a nonspecific finding which can be seen in both symptomatic and asymptomatic patient populations. In symptomatic patients, differential diagnosis includes infection, inflammation, migraine headaches, small vessel ischemia/vasculitis, demyelination, and very rarely neoplasia". While this very well could be due to migraines, I'm not convinced now that I've developed pain/numbness in my extremities and severe sleep problems. I do need to bring my concerns up to my doctor, but I feel as though I am starting to come across as a hypochondriac. I know I am not, but it may seem that way to my doctor. Thanks again!