If you're still having the same symptoms, I would probably stop taking any vitamin supplements and over-the-counter medications for 3-4 weeks to see if you notice any difference.

Vitamin D supplements could cause hypercalcemia in theory, but that's only supposed to happen if your blood levels of vitamin D get way too high. There are psychiatric/mental/brain symptoms that show up with that, though. Also, from the bit I've read, it seems like lots of physical symptoms usually show up along with the psychological ones.

As far as the doctors you saw not having a clue, it sounds like one of those situations where you have to keep going back and saying the same thing over and over until they send you to a specialist.