The same thing happened to me with the lithium. It seemed like it started working so well almost immediately and now so many of my symptoms are back. I'm also having pretty bad side effects and some toxicity so today, doc lowered me from 1500mgs to 1200 and upped my seroquel instead. Since I've only been on the lithium for three weeks, she says it's too early to tell if it's gonna work for me or not and I need to give it more time. I hope it starts working soon. I feel like I was teased for a week of being mostly symptom-free. Good luck!