Who do I need to see? Vision getting worse

I've been to the eye doctors, they keep saying I need stronger contacts/glasses. So I do.. 6 months, I need stronger ones. It's bad. I'm only 18! This started 4 years ago. Lately it's been so bad that I'm getting headaches everyday, all day. I brought that up and I just am not getting answers. I'm on my own so I have no idea where to go. What type of doctor should I make an appointment with? :/