The best thing to do is to go to a regular M.D. and tell him/her that you think you have parasites. S/he will give you a requisition slip for the lab. Any lab will look for ova and parasites. I am generally anti-medical world, but in some instances their Science proves useful. At least with tests you know what you're dealing with.
You can't take doo-doo out of the toilet and send it to a lab. It's contaminated already. You will have to collect it in a cup the lab gives you, and you poop into that the next chance you get. Then the lab will have also given you three tubes that you fill with poop to the fill line. Trust me, I've been all through this a million times. Until you have your stool tested you don't know what the problem is.