Anyone else experience this?

My jeans fit fine when I buy them, and maybe a little snug when I wash them but they stretch out. But then after 1-2 days of wear, they stretch out soooooo much that they are easily a size too big and they hang on me. Why is this? I don't think I could buy a size smaller because they would be too small in the store. Anyone else have this problem?

Re: Anyone else experience this?

This happens with cotton/spandex or cotton/lycra jeans. The saleswoman at Nordstrom told me that if they fit perfect in the fitting room, get one size smaller because they do stretch with body heat.