Sewingj if its baggy above your boobies chances are you need to use your upper bust measurement for your pattern 'bust size' then do a FBA for your full bust
I have to do this all the time because if I make to my full bust size its too big at upper bust, shoulders, neckline and upper back by using a size that fits my upper bust it all fits nicely in these areas
You would have to check that it would still fit your back, if back is currently OK then use usual size for back and smaller size for front
Its easier to do it this way than try to alter upper bust and shoulder area
JP