I understand what your saying I'm 14 and i'm on the heavy side too so the best stores to go if your an Plus size teen is Macy: go to the back and there is cute jeans and shirts there. Rainbows: there are great oversize clothes there and they are gorgeous.My favorite store though is Fashion bug they have all kinds of stuff for over weight people there from business to every day wear. I hope some of these suggestions helped you. :)
Old Navy, for jeans, Ashley stewart for tops. Also try Sears, and Jc Penneys, they have made great improvements on making cooler clothes for girls and tend to have a wider range of sizes. TIP: Go with a fitted look. Plus size doesn't mean wear big and baggy. Plus size always looks better with a more fitted look.