Argh! A whole post just vanished into the void. Okay. Here goes again. I have a few suggestions. I'd break this down into two problems. One is that you want to identify a definitive style for yourself. The other is that you may need specific ideas based on your IT shape. So:
1. Are there any posters on the form whose style you love for yourself? Key here is "for yourself." I love lots of folks' styles on them. It was a real lesson to me that I could love it, but not need to incorporate their style into mine. I love Alaskagirl (Una)'s style. Love love love! But...I'm in no way rough around the edges. So, I admire it and don't try to duplicate it. There was a great thread recently on getting some "edge" to your style where we all talked about this a great bit. If you missed it, definitely worth a read!
2. Start a Pinterest board that shows looks that you love and aspire to. It might help you identify unifying elements that will help you with your style. You might discover that you love colors. Or that you love neutrals and only really like colors to add a bit of pop via accessories. Or that you don't really like prints. If you can't make any cohesive sense out of your board, share it with the forum. You would be amazed by what strangers' eyes pick up that our own miss.
3. Start a Pinterest board that shows looks you love that include items you already own. I love having a source for ideas how to style things I already own. Whenever I'm in a rut, styling the same thing the same way again and again, I look at my ideas board.
4. Find other ITs on the forum. I always look at the ITs that I know because they help show me which shapes and pairings work well on an IT. I may not duplicate what they wear, but it informs me. ITs include me, Alaskagirl, Ironkurtin, AJ, Kellygirl, Carole, April, qfbrenda, Peri, Joy, MsKatieKat and probably a few others.
5. On jeans, oh jeans. Never pass up a pair of jeans that fit you because they are too long. Hemming is a fast and relatively inexpensive alteration. Almost no one finds jeans that are the ideal length off the rack. Think of the value of all the time that you will save by just hemming a pair of great jeans when you find them rather than continuing to search. It is really really worth it, just as much for cheap jeans as expensive ones. For the slipping issue, alas, all ITs are going to have problems with jeans slipping down. We don't have much in the way of hips to keep them up! However, denim with less stretch to it does tend to stay up better. Jeans without any spandex are as rare as hens' teeth nowadays, though.