How can I visit and pay for a gynecologist without my parents' knowledge?

In the past few weeks I think I may have contacted a VD and I am also about a week late for my period. We have no Planned Parenthood within an hour of my town and the health clinic requires you be from a low-income family, and my family doesn't fall into that category. I'm 18, but living at home with extrememly strict parents. I do have a card that pays for medical visits but it's under my dad's account so I assume he would see that I visited a doctor. Then I would have no way to pay for it.