Well, I've put on my asbestos panties's so here goes. If it was me and I was to the point I couldn't walk- I'd eat some meat for a certain time, say two weeks or a month, and see how I feel. If I noticed a big improvement then I'd know. If not then I'd know it's not from my vegetarian diet and I could look for other answers.
For the record (as long as I'm alienating everyone:)) eggs and cheese are not animal flesh. Providing they're from a good source, not a factory farm, giving eggs and milk doesn't hurt animals and can be valuable sources of nutrition. Especially if you aren't eating any meat.
Sorry to butt in, just my two cents. Hope you feel better soon.