Could Pain In Chest And Stomach With Itchy Anus In A Child Be Parasital Infection?

My son is 4 yrs old and keeps complaining about chest and stomach pain. He also always says his bottom is itchy all day long. We did a treatment for worms about 1 yr ago but the itching never stopped. He had a cold and is now getting over it. He was very congested about 1 week ago. His cousins who he always hangs out with had parasites in their stomach. I'm wondering if he could have got them.