maybe the contanst washing is drying out your skin and producing the spots. I know in the summer when I lie in the sun I usually get little white heads on my arms because my skin is drying out.
Try not to over wash and when you have a shower/bath exfoliate the area instead. Once you've dried yourself apply a good moisturiser. You need to exfoliate 2-3times a week.
It could also be a skin irritation from your legs rubbing together, do you see a difference when you wear trousers? If you want to wear skirts with no tights and your thighs rub together is can hurt after a while and you get a burning sensation. To avoid this you need to be applying a good moisturiser to the area, lap it on for a couple of days to build up the moisture in the skin and you'll find that when you go to dress in the morning you can cream your legs up and it'll prevent it all day.
I know someone who applies vaseline to the area when wearing skirts as vaseline won't soak into the skin.