How do you find a good STD clinic?

I'm not sure whether or not I have an STD... I am trying to find a free STD clinic... but I don't have a car... Planned Parenthood is like 20 miles away and there's no way I'm walking... ) How can you find a free STD clinic that is nearby... and how do you know if they are all right? ... Like I'm not sure I even have anything so I'm kind of wary about someone else sticking needles and things into me... like how do you know they are clean?? Are there any clinics you need to stay away from? ... Also do you need to call to make an appointment beforehand? ... I'm 17 so would it show up in my parent's phone bill? And how can they send the results... could they email them???