I too use to think I had a horrible memory, but now I know I only have a terrible memory when it comes to spoken words. My random facts memory seems to have deteriorated as well, as I've spent over a thousand hours reading such things and yet I can barely produce any of them.
“'Fuck', I think. What a beautiful word. If I could say only one thing for the rest of my life, that would be it.”
Ask me about yesterday today and I will have trouble with details.. Ask me about yesterday a month from now and I will recall details with vivid accuracy.
So I guess that means my short term memory is pretty crap.
My memory works very selective too. Some conversations I remember very well even with several years having passed, some actually word-by-word. Some odd passwords or numbers I remember like months or years later although I barely used them. Some study or school exercise solutions I remember still very detailed a year after when I get to do them again. Then again, sometimes I cannot even remember what I had thought or done 2 minutes ago, or when I had to do something very important and thought about it the same day, I will often forget it still.
What is also odd: when I think very much about one thing and then repeat it in my head for a few times, I sometimes suddenly start to forget what I thought about while doing so?