How To Treat Threadworms?

My son was diagnosed with thread worms and I convinced that I had them got treated with Pyrantel one gram dose . I got another dose because I thought I felt them again and I have now taken a third dose because I am convinced I still have them as I experience a weird wriggling sensation.My doctor assures me that after so many times of treatment they must be away. What is your opinion and what else could it be?