I don’t think you need to worry about the level of detail you describe to the priest. God understands where your heart is, and that you don’t intend to leave things out. That’s much less serious an issue than is that of avoiding occasions to sin, which is a key part of making a good Confession. St. Francis de Sales writes that a very important component of Confession is to have an intention to close off all occasions to repeating the same sin. Jesus said something similar, though more bluntly, when He said, “If your eye causes you to sin, pluck it out and throw it away.”
If you’re really serious about being cleansed of these sins, you’ll avoid the occasions for committing them. Right now, those occasions for sin are the role playing games, and possibly even the whole website(s) they’re on. Find some roleplaying sites that are PG-13 or some other creative outlet. If you keep on playing roleplaying games that repeatedly tempt you to sin, this suggests that you may be more serious about having a good time your way than you are about being free of sin. If sin is allowed to grow, it can become a very noxious and dangerous weed and can turn into even more vices.
So get out of it while you can. Close off the occasions to sin, all roleplaying in R or X-Rated environments, and look for a better place to roleplay, write or have a good time. St. Francis de Sales calls it a serious error in our Confessions if we Confess without doing what it takes to avoid repeating the same sins again, such as avoiding all occasions to sin, or in your case, the unhealthy websites or RPGs.
.