Am I Going Blind? [I''m 13 help!]?

Ok this started when i just stood up and then my vision went blurry so i shook it off. And now it got REALLY Worse EX: today the phone rang so i got up slowly and started walking then my vision got a little blurry then Very blurry and then the bottom half of my eyes i couldn't see out of it was black i tell my parents but there like Ooo Don't worry and i keep telling them and there like Stop Nit Picking at every little problem! and i get in trouble HELP PLEASE