Zz is correct, if you have a Tractor Supply Co near you, you can purchase Praziquantel, Ivermectin, Pyrantel Pamoate and other medications there.
You need to begin researching (googling) your issue, via your symptoms, visual ID of specimens you may see, locations on /in your body where they seem to congregate and once youve positively ID'd the species (compare to google images and member photos here on Curezone (under images, parasites, help identify), you can find out which anti-helmintic is most effective in helping to eradicate yours.
Im not telling you what to do. Im not medically trained. But you said youve already encountered resistence from the medical community. I do find it somewhat curious that you received that sort of response when inquiring abt pinworms as they are probably the most common helminth in the US.. Common in children.. Pinworms dont carry the social stigma that many of the other parasites do. Its diagnosed and treated more than other infections. Google "pinworm tape test" this is the common and simplest method to help determine if you have them. You might find that its something else entirely if anything at all. Its my understanding that a tell-tale sign of pins is intense itching of your bottom.. behind.. bum.
I got somewhat side-tracked.. If u determine u need medicine, and go to Tractor Supply or other pet, feed & tack store. Try and KNOW exactly what youre there to get.. Ask where their de-worming products are.. Get it and go. No need to engage in small talk with employees.. In other words, they dont need to know its for you. They cant knowingly sell it for human use. Though be assured that the active ingredients are the same as an Rx youd get if u could find a dr to actually write you one. Additionally, the "pet" variations come from the same Big Pharma manufacturers like Bayer & Merck and they bear the FDA approved advisement. Good luck. Were here if u need anything. Liz