Pants size and hip width have very little to do with pelvic outlet diameter, it's seems weird but it's true.
There is a thread somewhere with a gajillion different ways to measure your own bones, you don't need to go to an LBS and sit on their butt-o-meter. You can do it yourself with just a tape measure.
Terry saddles are generally on the wide side. Your saddle may be wide enough, but the shape or the padding may be causing you problems.
Before you buy any saddle it's a good idea to get your measurements (try a few ways of measuring) and puzzle out what about your current saddle is causing you the trouble.
Start a thread with your measurements, your current saddle, and the problems you are having; and I *guarantee* you will have several folks chirp up with suggestions to help!
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson