Worsening memory loss?

I asked a question a few days ago about memory loss possibly being a side effect from the prozac that I’m on, but apparently memory loss is very rarely seen with that medication. It seems to be getting worse. There are full days that I can’t remember for the life of me. I have trouble concentrating, I confuse dreams with reality and I can hardly keep my eyes open. I’m afraid there’s something wrong with my brain. I’m only 18 so amnesia seems a little scary to me. Any ideas on what’s causing this?