Definitely try Abercrombie or Aeropostale, but I love Seven for all Mankind and True Religion designer jeans, which come in European sizes and can therefore be found smaller. The most important part for making your butt look bigger is the wash- go fo...
To be honest, it means your butt isn't big enough. Don't worry, mine isn't either! LoL, sometimes I think that their portions are too unrealistic. They have large butts and slim thighs.
I wear a size 0 at AE, and a size 1 at Hollister. I've never gotten jeans at Abercrombie before, but they're the same company as Hollister, so they should be about the same size. A size 4 at AE should fit you (they don't have a 3), and a size 5 at Ho...