Sexual visualizations during retreats

I’ve been going to Vipassana meditation retreats for a while now. Every single time, I am plagued by sex idea and fantasies, almost like going crazy by it. During the sittings sometimes the whole hour passes with planning and imagining scenarios of sexual nature. Of course, the things I plan never actually get carried out once the retreat is over. But I am quite stumped at this pattern. Can you give me some insight on it, and an approach to manage/outgrow it? I should also mention that sadly I am not able to keep the precepts during these retreats- I end up “flying solo” multiple times . Thanks