I actually just went through the experience of having an external hemorrhoid. It was huge. There was no pain or itching involved, which I thought was strange. I was sent to a Colon Rectal Surgeon. He explained that it was a blood clot and would not go through your system if it broke. I had the choice of having them relieve it or just let it go on it's own. The doctor suggested I just let it go, but it was my decision. It is more painful for them to do anything with them. I was told no excerise or heavy lifting and to stay off my feet for a few days. Laying down was a must. If I had any pain then I had to go back. Well mine healed on it's own. In your case you should see someone, as you are experiencing pain and itching. As for the dirt on your underwear, the doctor told me to expect that. You really need to have it checked to see if it's external or internal. It does take awhile for them to subside. Mine took 3 weeks. Good Luck and I hope you get the answers you need!
It definitely sounds like a hemorrhoid. Use the medication as prescribed and if it doesn't get better, see your doctor. Use a cortizone cream for the itching, the itching just keeps it irritated. Hemorrhoids grow and shrink, and I'm sure the cream was shrinking it and when you stopped using it, then it swelled again. You probably developed this from being constipated. You can actually push it back inside the anus with no problem. I think it may be time to have your pediatrician take a second look, and if you get no answers, see a Gastroenterologist. Take care...