Hi! I'm not bipolar, but I have BPD and am encountering a similar situation. I'm only 22, but made straight A's in high school when I wasn't on meds; started my first med at the beginning of college & my grades suffered a good bit, started making everything from a D, several C's, mostly B's (barely) and only a few A's throughout my four years, taking an average of appx 15 hours a semester. Now I've just finished my first semester of grad school, on a cocktail of 3 meds, with only a 12 hr load of what I would have called "easy" classes 4 years ago, and i barely passed each of them.

Long story short, I noticed I do feel "dumb" also. I have a VERY hard time coming up with words to use in daily conversation and usually need people to repeat what they say several times before I understand. It's the same with reading, I take two or three times as long as i used to because I have to re-read everything so many times to gain understating.

I now take 100mg of Pristiq for depression & BPD, 30 mg of Vyvanse for hypersomnia/ narcolepsy, and 1mg of Klonapin for anxiety/ panic attacks.
After a stint of "musical meds" in an attempt to find the right one to treat my sleep disorder (100-200mg of Provigil, then 125-250mg of Nuvigil, then 10-40mg of Ritalin, then finally finding the winner at 30mg of Vyvanse), I did some research on drug interactions. Doc willingly prescribed me the Vyvanse upon my request, since nothing else had worked, even though i thought it'd be a long shot since all the websites I had read gave Vyvanse & Pristiq together a huge red flag on interaction. Paranoid my dr wasn't knowledgeable enough about his job (bpd lol) i did even more digging and found that apparently with the two meds taken together there's a "small chance" that the consumer could develop "serotonin syndrome" from taking them both together. Guess what, it accounts for all the memory loss, confusion, etc. etc.

Not saying you might have serotonin syndrome also, haha, but looking into your potential med interaction consequences could maybe give you some insight like it did for me! I am unwilling to stop taking any of my meds also and resistant to going through the daunting process of changing them; so i've just decided to deal with being "dumb" haha. You might be wanting to take a different route though. Anyway hope some of this helps!!