Well, from what I've read - too much b-complex can be a bad thing because B6 can cause problems if you overdose. But B12 ALONE - I'm not an expert - is usually reported as safe at high levels.
You may be experiencing more pain because you stopped the B-complex, which had B12, which you aren't getting now.
So maybe you could try JUST a B12 supplement (without the "complex")?
I take one B12 "dot" daily (500 mcg) sublingual (under the tongue). Plus I give myself a monthly B12 shot (doctor prescribed).
Also, ask your doctor which B-vitamin he thinks is too high. If it is not B12, you should be able to keep taking it by itself. If your doc says it IS the B12, ask him why he thinks it is dangerous. Maybe he knows something we don't?? I'm interested to hear the doc's rationale.
Liz