Uncomfortable in my new Yaris

[LoCodder]

I bought my Yaris in October last year. (2009 model). By January i was feeling serious pain in my tailbone so that no position in the seat was comfortable (wow this post will be rife with "that's what she said" references i think). It got to the point that when I went to the gym I couldn't sit up with my legs out straight to stretch. I'm just searching the web to find out if anyone else is having this problem. I now have to sit on a folded up towel to relieve the pressure. This has worked and I got rid of the towel. Well now the pain is starting to come back, that's how I know it's the car. Is anyone else having this problem? I've read posts about uncomfortable distances etc but didn't find anything regarding pain. I'm a normal sized 30 year old female. Not overly tall or short, heavy or thin. My doctor agrees that it's the seat, but says there's not much I can do besides buy an expensive ergonomic cushion. That seems excessive.