Is there a way that someone can become incredibly stupid because of external problem?

You know that character from movie or story that always make a mistakes and screwed up even at a simplest task? I’ve become that person. I don’t know why but I feel whatever choice I make or anything I do always end up wrong.

I wasn’t like this before, I don’t want to be sounds like conceited but I was performing better than most of the other student in school. It just keep getting worse each day. I kept forgetting things, I didn’t remember someone say something to me but they say they did, etc.

Is there any connection between my stupidity and my (self diagnosed, I haven’t go to psychologist) Bipolar Disorder?

And there is a family issue, financial crisis, and college stuff that happen in my life. But are those can really affect me?