"Not much" has changed? It doesn't take very much to radically alter the fit of your bicycle. Do you still have your old bike? If so, take a tape measure and carefully record the lengths of the top, bottom, down tubes, etc. The distance between the center of the BB and the top of the seat is critical, as is the distance from the center of the saddle to the point where you grip the 'bars. Don't forget the difference in height between the saddle and the handlebars. If you felt comfortable on your old bike, try to reproduce its fit on your new bike as closely as possible. Also, if your new saddle is uncomfortable, you may be unconsciously raising your behind up off the saddle. This puts more weight on your arms and wrists, and forces you to tighten up your back and stomach muscles to support your weight.