I had the same problems and then some, while on lithium.
In 6months I was dumb as a rock, couldn't remember, spell or form intelligent thoughts anymore, my vocabulary sucked. I knew very few words bigger than 2 syllables and I got plenty definitions messed up when I did remember them. I even forgot some pronunciations.
Pdoc first seemed disinterested, then blamed my bipolar, and later he all but called me a liar, because meds can't cause the type of brain damage I was describing...
Took two years post flushing the meds down the toilet for my brain to heal, and thank God it did.
I could NEVER live like that, that's a hell in and of itself.