Good to hear that you're thinking about more reliable methods of birth control! You can buy multiple methods over-the-counter such as condoms, internal condoms, the sponge, and spermicide. However, the most effective methods are only available after a visit with the doctor, so we hope you'll think about making an appointment. At the very least it's good to be getting annual exams when you're sexually active.
Try searching for low costs clinics, if you don't have insurance coverage. And while you're there for the appointment, you might as well talk with your provider about your birth control options, right?