Hey Abbey,
Be sure to keep all your test results and MRI copies in a notebook. You could add to that a few (non-emotional) notes as to your symptoms and the time when they occured.
I would want a definitive answer to why you have 3 or 4 white matter lesions on your brain. Do you have a history of migraines? Did you ever hit your head or receive a concussion? Your symptoms could be MS. Your symptoms could be something else however. The whole description of your leg being numb and then sometimes better depending upon your position sleeping sounds more like a pinched nerve. What with all your back/disc problems, diagnosis is going to be complicated.
Certainly the D3 will help. I take 4,000 IU a day. So do my children. The D3 has really helped me. If your levels don't come up on your next blood test, ask the doctors to be very aggressive. You can take much higher doses. You can also get some sun everday. Get as much of your skin exposed to the sun for 15 minutes as you can (without sunscreen). Just be careful not to burn. There is no sense in adding skin cancer to the mix.
If you aren't better in 6 months, I would ask to revisit MS. Meanwhile, try to relax and be positive. Exercise as much as you can however you can. Eat the very best foods you can. Take your D3 and get plenty of rest. You are free to email me if you want. I am always available.