It could be the Lamictal that's tweaking your short-term memory a bit. It's a common side effect. You're at 200 mg/day, which is thought to be a therapeutic dose in most cases. I'm on 400 mg and I feel dumber than an entire bag of hammers, but it's better than having the wild ups and downs on the mood spectrum.

I guess all you can do is ask your doctor if you can try it, but as you know there is always the possibility of getting manic. Maybe he'd let you come down a little on the Lamictal rather than risk putting you on a stimulant. Call or go in and see him as soon as you can. His opinion is worth a lot more than that of strangers on an anonymous Internet forum. Good luck.