I think I may have a problem...

I dont know I'm on this depression medicine and I know there's a couple side affects like forgetting things...I mean I'm already horrible at forgetting things but its a lot worse. Sometimes somebody asks me something and I reply, then I think to myself..."what did they just ask me" and ask them what they asked me....if that makes since....please don't judge me but I didn't finish school. (senior year) I had a lot of things going on. I wasn't the smartest and I wasnt really good at chemistry. I want to get my ged and I want to study for it...I'm 20...I feel like ive forgotten everything and I dont know how to approach to study for it. I feel like I'm so stupid and my memory is horrible....any advice please....