I think your problem is due to poor UV mapping. In this screenshot the dress on the left has a simple UV map with viiews of the front and back of the dress. The polygons at the edges of the views are distorted and the texture gets severely distorted, The other version has the dress split into 11 different panels along the lines where there would be seams in a real garment and the parts are laid out as though they were on a length of cloth ready for cutting. This gives a much better result with no stretching. The discontinuities in the pattern (eg round the waist) occur where they would on a real dress and look natural.