I'd trade those Trackers in if you can ... I had a pair, and they didn't hold up. they also don't provide as much protection as some other models.
As for shorts, I wear a pair of Moose padded shorts, and usually no panties or a thong. I don't have any bikini-cut or boy-short underwear that doesn't crawl, so I just try to eliminate the problem to start with. Besides, shorts + panties = one extra layer that do you really need??? LOL (this thread may go downhill fast). Anyway the shorts fit great, and do not creep or create wedgies. If there are any women's specific shorts, you may have to shop for them from a bicycle manufacturer, but the Moose shorts seem pretty unisex. They're spandex so they will conform to your shape, and it's not like there's a built-in cup or anything.