Check this out- it will help you.
http://www.iwannaknow.org/basics2/
It has information on pretty much every std and how to prevent them, how to get tested, how they can be transmitted, etc. Read it all through before you continue having sex!! And I agree with marvel, don't assume you won't get aids. There is no way to tell if your partner has HIV unless they tell you.
Planned parenthood does std screening and treatment without parental consent, and usually at a low or free cost if you don't have any money (most 14 year olds don't).
I suggest finding one and taking the bus there or getting one of your older friends to drive you. And take your girlfriend, and she might be able to get some birth control, too.