I've got to get new jeans

I love these new jeans from Lane Bryant but they tend to get really lose (they stretch a bit) after an hour. The size I bought fit perfectly when I tried them on but now after an hour I can pull them right off my hips without unbuttoning them. I am going to buy a couple more pairs but I think I will get them two sizes smaller. It's crazy, these jeans fit wonderfully but after a while they are so baggy.