Skinny jeans suck. There should be a ban on skinny jeans. People who make skinny jeans should be thrown in jail. Skinny jeans are not for skinny people they are for weak people. Women who have legs that can actually accomplish things can't fit into skinny jeans. What they need are big thigh, realistic waist, no gap in the back jeans.
If you gain size in an hour it is probably water or swelling from inflammation.
Women need fat on the hips and thighs to provide the correct healthfulness to carry a baby to term and beyond. We are disposed to fat there and can't really do a lot about it. All you can do is get your whole body to a healthful weight and then try to be satisfied with what you've got. Strength training can help make it jiggle less and make you feel better about yourself. (Unless you take it to an extreme and try to do something nutty like obtain 15% body fat.)