I was then moved to do a bit of research, and found a blog post called Lamictal (lamotrigine) withdrawal from hell. Hardly an encouraging title. Hell, I'd even say it was terrifying. But I was brave, and my courage was rewarded with a ton of useful information, including extended quotes from other lamotrigine users (and former users) describing the incredible fatigue they experienced as they weaned themselves off this medication. In order to combat this (and other side effects), many of them found that they needed to return to the higher dose for awhile, then lower the dose more gradually, over a longer period of time.
On Sunday, I emailed my doc and we decided that I'd go back up to 250 for a week. My fatigue has gotten better, but on the downside, I've had trouble sleeping, and I've felt more agitated. I've decided to try going down to 225... we'll see what happens.