Serious question

This might sound dumb but why am I not smart.?!? I’m 19 trying to get my GED and this is basic stuff I still don’t get it.!! Even in back when I did go to school I hated it because I was always so slow n confused.! I’ve never failed a grade only when I got pregnant n dropped out my senior year. I try to study but I don’t get it at all no matter how much I try to study I don’t get anything I feel dumb n my memory sucks so bad I legit don’t even remember some of my childhood even some of my early teenage years. I forgot how to even divide.! 😓