I had fistulotomy yesterday due to anal fistula. I used to warm sitz bath 3xday. But I have recurrent varicocele. How to prevent worsening?

One at a time. you do not worry bout your varicocele while you are recovering from fistilotomy the sitz bath are important eventually after you heal completely you can start worrying about your varicocele. concentrate on getting better.
Shouldn't worsen. Keep the fistulotomy site clean at all costs. The varicocele shouldn't worsen. Consider however using a hand held shower head for cleaning the wound with warm water. If the baths are bothering the varicocele, this may help. Also, ok to use hand held shower head more than 3x per day. Be sure to follow up with your surgeon as well. Hope this helps!