Hi Encore, I'm 5'0," also have a little pot, and have the baggy seat issue too, because I don't have much of a butt or hips. For reference, my waist is 28 inches (27 on a good day) and hips only 33 inches. I gain weight in my stomach and upper body long before I gain anything in my hips, butt and thighs.
I have tried on just about every pants and jeans imaginable, and my best bets are:
1) For jeans, try Citizens of Humanity. Try their Elsons (straight legs), Ambers (boot cut), and Huttons (flared - kind of like a trouser cut). They do have a bit of stretch, but not so much that they will stretch out horribly after the 1st wear and leave you with baggy butt syndrome (BBS).
You might also try Earnest Sewn for skinnies, however, they are lower rise than the COH I listed above. Earnest Sewns I have barely stretch at all, and there's something about the cut that prevents them from sliding down off my hips, like most lower-rise skinnies tend to do.
2) For dress pants, try Banana Republic Martins in petite. These are the best fitting dress slacks I have found, hands-down. Look for styles that have a thicker waistband - the wider waistband will "lock and load" your trouble zone.
If you want jeans and a lower price point than COH, you can also try Ralph Lauren petites. Their denim doesn't stretch out, and they tend to be higher rise. However depending on your size, you may be out of luck. Since losing weight, I can no longer fit in their smallest size.
Inc brand at Macy's, in petites, can occasionally yield good-fitting pants and jeans too... However the quality is just not as good, unfortunately.
