It also sounds like it might be a skin yeast infection. I had one that started in that area and spread very quickly. It doesn't matter if it is a fungus or a yeast, though, because the treatments are the same. The tea tree oil, grapefruit seed extract, and gentian violet are all excellent ideas. I can see your point about oil of oregano being very strong, but it is also very effective (although, as you say, you may be reluctant to use this if you are pregant.)