In my humble nocoach opinion, Mastering breathing is not a light issue like learning to use some muscle or changing a timing. That's why I think that you should not rush it and just do "baby steps". Just let it be until you are comfortable with it. Better be careful than do it wrong or losing it. It has nothing to do with you. Its just how it is.
I may be wrong and you already master it well enough :)
you must be a donkey before you become a dolphin.