I bought a pair of Levi's denim leggings last year - they're really skinny jeans, I guess, because they're real denim and have a zipper and pockets. I went up a size from my usual and they seemed to fit very well. But every time I've worn them, they start sliding off my hips very soon after I put them on. Not so fab to be hitching my pants up all the time, but I think one size down would be too tight on me. This happens with regular leggings too, but to a lesser extent. Anyone else have this issue, and how to solve it?