M..
My daughter got pinworms last spring (I think from her babysitter at the time). One dose of the medicine (plus washing everything in sight) and they were gone. A local school had an outbreak from a sandbox at the school. Its really gross but it happens. It is highly contagious, yes, but with the meds and washing all the bedding every day for two weeks and you should be fine. Best of luck to you. Hope your little guy is better soon!