If it's worms, then it's pretty simple to get rid of. You take a small tablet and they are gone in about a week...maybe another pill would have to be taken and go through a second week in a really bad situation. It's fairly easy to get worms if you are around a place or person that is infected. You can even breathe in the eggs, so it doesn't mean you should be embarrassed about it. Just tell the doc.
Other than that, sometimes, you just itch. Part of it might be because you don't wipe the bowel movements away well enough. Sometimes if there is even the slightest little bit of waste there, it can irritate your skin. This most often happens with constipation. I would suggest getting pre-moistened flushable wipes. That should help.