Hi Lakefield Girl,
If the odor is that strong or unpleasant it may be that you have some kind of infection of some sort. You should really go see a doctor/gynecologist and have an examination. Some infections may not be painful so they go undetected, but they can cause damage, even infertility or other medical problems.
No matter what I strongly encourage you to get a gyn check up. In the mean time, to clean externally I've found that using a cheap shampoo cleans really well in that area. Shampoos are designed to break down body oils easily, I like nice fruity ones. I lather well in all of the folds and creases, making sure to lather well where my thighs meet the pubic area, there are many sweat glands there.
Take care, see your doctor as soon as you can
