I'm sorry you are having pain with your seton. I m currently wearing my 2nd one and it does not hurt. I barely feel it.
The 1st one I had in (it was taken out and a fistula plug was put in last Jan.) was very painful-it was really close to the perineum and hurt all the time. I think it was probably the location. for me but if the area is infected and you are getting abscesses despite the drain, that can cause pain too. I have had my drains "back up" so to speak and that definitely makes the area a bit more sore.
Are you doing lots of sitz baths? Don't skimp on that little luxury (lol) because that really helps the healing process and comfort level.
Feel free to email me if you have any questions-it's in my profile. As you can see from my signature, I have lots of experience with these nasty fistulas.
Feel better soon.