As your body grows and changes, things do change size at different rates. To add to the fun, the manufacturers don't stick to standard sizing - and that counts not only for the overall size of things, but for the particular measurements like waist size and thigh width.
The best thing to do is to ask for help at the department store - preferably from the lady with the most little pins on her badge. You want those years of experience on your side. They know what each brand will fit each body type- and when you find it, buy a few of whatever it is so you have it. Sometimes the next year won't fit the same way...
One thing an experienced clerk taught me was to never go by the size category. Some tops in Petites fit me better, and I am not short at all. Sometimes things like tights do need to be a plus size, even if you aren't chunky, because they give you a bit more room in the waist- so ask the clerks, and try things on whenever you can - and stay out of places like Old Navy, where they don't have that kind of service, and buy in bulk from the poorest of countries on vague contracts. That's not where you will find the best fit, ever.
That having been said, you might try some Lee Platinum jeans. They have some stretch to them, but are still real jeans, and cut for bodies like ours. They aren't baggy, but do give you room. Have a local seamstress measure you properly before you order anything or go shopping- that can also help a lot. And if you order online, you can also call their customer service people - if you have your measurements handy, they should be able to help you find your proper size.
In addition to that, if you do buy anything online later on, look at the review first. Sometimes a product will fit true to size, other times they have a specific problem. You want to know that first before you spend the time and money ordering it. On the other hand, if it's something you already own from the current year, you may be able to order more on sale, and make out in the deal.
But - back to your original problem. That skirt isn't going to do anything for you. Don't get hung up on trying to make it work.
Look for a few really good things that fit you well - it is *never* a bargain if you can wear it, or it doesn't make you look great, or for that matter feel great...these are my secret weapon.
http://www.lee.com/store/LEE_STORE_US/en_US/category/collections/for-her/platinum-label.html
As for dressing more femininely, top those off with a ruffle sweater or a tunic top that looks more like a short dress, and you have it made:
this place sounds like they would sell pull-on pants, but they do have some very pretty long tops for over jeans that are quite feminine:
http://www.softsurroundings.com/On_Sale/?aid=ga.branded&cm_mmc=google+cpc-_-%28ROI%29+Branded-_-Sitelinks+Extension-_-soft%20surrounding&gclid=CJjM7ezrrb0CFUoV7Aod9EQA-g
Hue tights seem to fit better, and may even be on sale now.
But look into getting a size bigger than you think you take- and go by the measurements. You may be better off waiting until summer to wear dresses, so you can skip them altogether.