The easiest way to tell if your B-12 deficient is to get a blood test. I'd suggest getting a full B-panel done. Make sure not to take any B-vitamin supplements for about a week prior to the test or it'll be skewed.
There are a lot of things that can cause B-12 deficiency, such as a vegetarian diet, some meds like PPIs for acid reflux, and malasorbtion conditions such as Celiac. Just so you know, neuropathy is one of the symptoms of Celiac so it might be something to look into.
Good luck and please keep us posted.