Down here in the Deep South pinworms are pretty much endemic. Don't be embarrassed. It happens more often than you think. Lot of times the eggs live in sandy soil and playgrounds. Kids pick them up when they're playing outside. If they don't wash their hands they ingest the eggs where they hatch and multiply. The itching is caused by the little worms laying their itchy little eggs. Then the child scratches, gets the eggs under their nails, doesn't wash hands, and the cycle continues. They can also pass them to their friends this way. I know, gross.
However, there is an over the counter med, Pin-X, that you can buy at most of the chain pharmacies, grocery stores, and
Walmart. Give it tonight and wash all the linens and bedclothes in hot water in the morning. If you have other children it would probably be a good idea to treat them too.
Honestly, if I had my choice I'd rather deal with pinworms than lice. One dose of medicine, no combing, and you're done. Best of luck to you. We went through this with Christian one time. Blech.