You mentioned that the flat breasts are only for your character? Do you have any mods installed that make your character body/animation different from NPCs? I've seen at least one mod that does that, if I'm not mistaken. Additionally, as Anjenthedog said above me, you need a preset and to run FNIS after you install these mods. I sometimes used to forget to actually run FNIS as a program, not just a mod in the game. Hope this helps, good luck!