I am rather small (5'6 115) as well and have always had a hard time finding clothing that fits PROPERLY, but i have found designers that suite my needs:

Bottoms: 7 for all mankind, BDG, Rock & Republic, THEORY, Polo slim fit, Zara, Burberry slim fit, H&M, The new Lacoste slim fit

Tops: THEORY, Burberry slim fit, Polo, KOSTYM(cheap monday's nicer brand), Lacoste, Hugo boss(designer sucks....but they make very small sizes)