You should find a pdoc and quit volunteering. You work a minimum of 66 hours a week and take classes. It's no wonder you feel like you're losing your mind. The organizations you volunteer with will be fine without you until you're done with school.

I'm sure you've thought this out, but if you can make any changes to decrease your work hours that would be helpful. Maybe your wife can work part-time so you can quit your second job? Or take in a kid or two during the day to watch? It sounds like you live in a rural area, so I'm not sure how feasible that is.

Don't feel like you're skipping out on your doctor. What's going on with you isn't caused by a vitamin deficiency.