I used to have one nightmare over and over when I was that age. I grew out of it. Didn't need any exorcism or other magic.
Amazing how superstitions, like thinking holding a rosary will keep something bad from happening, get engrained in us.
When I was about, oh, 11 or 12, I became enmeshed in a perfect storm of superstitions, beliefs and religious terror.
I was too young obviously to read it, but I somehow got my hands on "The Exorcist" and read it. I wasn't at all convinced at the end of the book that the little girl was safe. Right after reading it, I was in church one Sunday and the sermon was being given by this horrible old alcoholic fire and brimstone priest who told the congregation how the devil could enter us at any time, and thinking about it increased the chances. While sitting there, I suddenly felt horrible, and was convinced I was being possessed. No, I was coming down with the flu. For the next few weeks, I battled Satan, knowing he was just toying with me.
No idea how, but somehow I got hold of the information that this medallion of Mary, if worn, would prevent a person from going to hell if they died, and if they said the prayer on it every day. I'm sure I said the prayer a hundred times a day. I remember looping black twine through it and wearing the stupid thing every day for months. Heh, I should investigate where I came up with that one.
I was an unhappy child before all this, and this really sent me over the edge. The ******* things we teach people, and that we believe.