There are child psycologists, but you should be able to visit anyone. I believe a child psycologist would be trained in talking to a child who wouldn't easily communicate. If you feel you can communicate your concerns as an adult, you would be able to talk to a regular psyciatrist/psycologist. You can call them though, and ask if it's fine for you to come on your own without a parent. You should talk to your parent though, to make sure of your medical coverage, otherwise you would need to know the rate to pay in cash.
What country are you in? Look under pediatric psychologists or psychiatrists, they're ones who specialize in people under 18 (sometimes up to 21). Since you'r 17, you could probably get away with an adult doctor, though. You would want to see them in person, not over the internet.