Yes, I think you should aggressively take the oral. 5mg a day of the methyl on an empty stomach. Obviously the injections are not doing well for you.

In answer to your question about fluctuating levels I think 3 things.

1) Because the injection only lasts in the body for a very short time, getting them every 3 weeks before you are stable is not enough.
This link illustrates the rapid clearance of B12 in an experimental situation.
http://www.ncbi.nlm.nih.gov/pubmed/15730428


2) B12 is stored in the liver. So when you get that infrequent shot, the liver is sucking some of the brief blood levels.

3) There is an active transport system into the cerebrospinal fluid. I works better when the blood levels are HIGH, thereby a gradient of sorts helps get the B12 into the spinal cord and brain. When there is a low amount in the blood, the spinal cord has less to get it needs from. If you take a high dose DAILY, then you will get better serum levels, so your nervous system can heal better. About 10% of the oral dose is absorbed passively in the intestine and daily use will cover the short half life and provide a steady amount of B12 daily, instead of peaks and valleys.

Since B12 is non toxic taking the oral in high doses is not harmful. Just make sure it is on an empty stomach because food interferes with absorption, and you want as much as possible to be absorbed without intrinsic factor. The oral form is not expensive either. Luckily both factors work in your favor.

Once you have damage to the myelin in the spinal cord and brain, it will take a longer time to fix if that is even possible.
Using methylfolate and B6 would be helpful for remyelination, because they work in concert for repair.

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