I've been tortured by this over the last couple days.
A few months ago, I did this thing online where I sexually role-played as my sister, showing pictures of her (non nude or anything) to random guys, pretending to be her cybering and masturbating. This randomly came to my mind again and I can't get it off my mind, I'm just extremely ashamed of it and I don't have anyone I can tell who won't judge me or will help me. I feel like I think about my sister too sexually, I kinda always have. I haven't done it lately, though, I've come to my senses.
What can I do to alleviate this? I can't stand having it on my mind but I really shouldn't tell anyone.