Dosing once B12 Levels are high

I have all the textbook sigmotoms of B12 deficiency.

I have a question regarding dosing once B12 levels are high again. I started with 5000 methyl mcg daily, I was not feeling better so I doubled it, and upon doubling some of my old symptoms started to return and my current symptoms started to get better. I have roaring ears and with every 12000 dose my ringing would decrease a decibel. After testing, my doctor informed that my B12 levels was high at 1800 and that I should stop supplementing. I do not want to stop because large doses has been the only thing that lessens the ringing in the ears and head and memory problems.

My question is If B12 excess is supposed to be flushed out of the body how could my B12 number be so high? I started doubling my B12 to 12,000 right after taking the blood test so if it was 1800 then with dosing at 5000 mcg daily, what would be my level be now with 12,000 dosing? Can one coninue high dosing after achieving a high B12 and still be safe? If you have any insight into this I would really appreciate your input.