All the girls have covered positioning well - give those a try for sure. You probably already know about the correct body position, but I'll post just in case you or someone else reading doesn't know this one....

Be sure that your pelvis is quite vertical, keeping your weight on your sit bones, and that you bend over at the waist and keep your core engaged. It took me a long time to figure this one out, and I'm still poor at it when I'm fatigued. Mainly this is because in all my stretching, yoga, and other exercises, I learned very well to always bend at the hip, not the waist. When you do that on a bike saddle, the weight rests (not-so) nicely on the soft tissue. Ouch!

So it's likely a combination of any or all of the positioning and saddle comments.

If you've got the will to work on your own, you might do better to buy a trainer and set up your own bike in your house. Works for me.

H&B
~T~