My eye's a bit blurry?

It's been like this since I woke up this morning (I'm 16, by the way, so don't go suggesting I've got some sort of adult or elderly person problem!). At first, I thought something was in my eye, like gunk or some wateriness or something, but it just wouldn't come out.

When I shut the good eye, I can kind of see two of all the words I'm typing. When I shut my blurry-ish eye, everything's perfect.

I've never had problems before - in fact, I've had perfect vision my whole life.