The pain you describe can come from either the saddle being set too high, so your girly bits rub in a sawing motion as you pedal, or from the saddle not being wide enough to support your sit bones so your girlie bits are supporting too much weight. Compare the saddle height and width to your road bike. If the cranks are longer on the spin bike, you'll need to lower the saddle by the same amount, you want to keep the distance the same from the top of the saddle to the pedal on both bikes.