There are lots of reasons people get abscesses in their anus. My husband got one when he got his apendix out, he was 13. So to say it caused it then was the best answer the Docs could give you. Perhaps another illness, then the pus pocket? Kind of sounds a bit like toxic shock syndrome from tampons? Just wanted to get you to look at it different. We've all done things we regret, I'm not convinced poor judgement at a young age regarding anal sex was the cause. I was told at 15 I had a bad appendix they took it out and I got a horrible wound infection. My pelvic area was full of infection they discovered and came up with everything from gonorrhea to staph. I believe it was toxic shock......