Why have I become so forgetful?

A few months ago I noticed that I was forgetting things alot which made me look really stupid, I get trouble remembering the simplest things that I did even things I did a few seconds ago which is so frustrating. I never used to be this forgetful but now all of a sudden ill be talking to someone and ill even get words mixed up and not even notice what im saying until someone points it out which is embarrasing especially when it happens more than once. Im 15 by the way.