Are you taking Topamax?
This medication is fairly well known to cause many people "cognitive dulling."
Surely, other meds used to treat bipolar illness can have similar side effects.
And if you are menopausal, this can make things worse.
I would talk w/ your doctor about your worries. If you are taking a medication known for causing cognitive issues, I would ask for a reduction of this medication. Some folks have taken Aricept, not because they have Alzheimers, but because their medications interfere with their thinking. There is a natural supplement called "PS" that helps many with this issue as well.
Fish Oil can provide all around help.