Number one, it depends on where you go. I would recommend a drug store or walmart. You can usually get deals where you get two for the price of one.Most pharmacies carry multiple kinds, and to be honest the off brand products work just as well as name brand ones. Walmart's equate brand works just fine if you don't want to spend the money on EPT or any of the others. Price ranges are normally from 7ish dollars to about 15-17.99. Really it's up to you on how much you are willing to spend...but the cheapies do the same job as the more expensive ones.
Hope that everything turns out alright, I have had a few scares myself. Good luck with everything!
On a sidenote....if you are seriously worried about it...have a doctor check you out, and if you are worried about confidentiallity, then don't....there is nothing to worry about there. Like I said, good luck, I am sure that everything will be okay for you.