You don't always get the nausea, vomiting, or diarrhea as symptoms, especially if the toxic levels builds up over time. To me it didn't feel real bad or anything but something was obviously wrong.

And what you listed are all symptoms of lithium toxicity. Please don't try to wait it out because if it is the lithium you could have a seizure, coma, kidney failure or die. If they catch it right away it can be managed pretty easily in a lot of cases. Even of you have been on it at the same dose for a long time, can easily happen.