Well, since you are over 18, your medical records are now YOUR property, and your parents (or anyone else) are not allowed to have access to them. This would include anything you reveal to your doctor in the process of an examination. However, I can understand that it might be awkward to see a doctor who knows your parents -- my first GP was a friend of my parents and I always felt awkward about discussing sexual issues with him. Even if he isn't allowed to tell, there's always the issue of feeling like he might, no?
It is really important that you do get access to regular sexual health care -- it'd be far worse if you didn't and something minor went untreated and became a major problem. Do you have access to a car or public transportation that could get you to a Planned Parenthood clinic or other sexual health clinic in another town or city? Do you attend a university that has women's health services available? (Your insurance might cover services there -- check and see -- or it might be reduced cost for students.)
You also might want to just talk to your parents and explain that you're concerned about your health, that it's important that women who are past puberty get regular gynecological checkups regardless of whether or not they're sexually active (being sexually active just makes it all the more important), and you'd like to see the gynecologist and have them respect that. You don't have to say "mom, dad, I'm having sex" -- just make it clear that you'd like their support in helping to keep you healthy.
I think you can hopefully find a Planned Parenthood near you (use the clinic locator at http://www.plannedparenthood.org) and then get some confidential care. That might be a good short term solution.
[This message has been edited by ErinK (edited 12-01-2002).]