Make an appointment with Family Planning or Planned Parenthood. You can search for a Planned Parenthood near you at www.plannedparenthood.org. They will explain all of your birth control options and give you whatever method you do end up choosing.

if you have planned parenthood then they are great for b/c
they are also confidential

You could also pull the "I want to make my periods easier" or "I want a b/c pill for my acne" or "I want to be able to control when my periods come" excuse for your parents. If they are smart, they will listen and not ask questions. Plus, most pills really do most of these things, so it's not really a lie.

If you don't want to do that, planned parenthood is confidential and they charge on a sliding scale so if you have no money you won't have to pay much. And once you start having sex, you should be getting an annual exam from a gyno. At your annual they also usually prescribe birth control if you need more. They do this at planned parenthood too.