You're the first person I've seen that has a reaction to b12 like this, aside from me. I have a very very bad reaction to b12 and tried numerous forms of it and at varying doses. Bcomplexs and multivitamins did it to me too. I learned after months of trying that b12 was not an issue and to avoid it like the plague. At least for the time being...
methylb12 was the worst and strongest.