Eyesight worsening? PLEASE HELP?

Im 15 and my eyesight has seemed to get much worse the past year. I went to an eyedoctor in august and he said i had slightly poor vision and i can get a perscription if i wanted to but it was not necessary. I did not and now my eyesight has seemed tto get worse. I cant read the board in any classes and i must strain to read anything remotly far away. I am alright with reading books and stuff but its things far away. I am afraid i am going blind. Please help