problem with brain function and pain in legs.

i am a 19 year old male in canada and having problems health wise

ok so i am difficient in b12 and have been taking supplements 5000mcg for 2 months now and so far recieved 4 shots of 1000mcg
my main symptoms are
black outs .... when i am laying down or sitting and i get up every hting sometimes goes black and i cant see
memory recall
extreme concentraion problems
cant think of new things/ideas
brain fog
mental lethargy
muscle weakness
musucle spasms
pain in my hand and arms like needles
leg twitches and spasms
muscle spasms
serious zoning out
anxiety
palpitations
Problem thinking i can think clearly ...its like are big breaks in my thoughts and my brain sleeping or something

ALso when i feel i have leg spasms or twitches its like at that time my body wakes me up. because what i feel happens is my brain is shutting down or something i am zonning out and there is no thought in my head at that time and den my body jerks my legs to sort of wake me up

also i feel like these symptoms have been there for at least 2 yrs and now slowly they are becoming worse

what can all this mean i have been to my doctor and he said it cuz of b12 ... now i have a appointment with a neurologist coming up... and my doctor said that we'll try another 2 shots of b12 and den they will write me up for a mri and cat scan or something like that.