Kate, If you have tried a 32D instead fo 36B you have simply gone for a smaller band and not increased your cup size at all (a 36B on tight setting IS a 34C and 34C bra on tight IS a 32D hence you have not increased your cup volume by changing a 36B for 32D!!) Try something like a 32FF (try it: it may sound big to you, but actually only an average size cup!!).
Problem is that your coopers ligament have been damaged from years of wearing a 36B (which visually is an average to wide man with a nipple but no boob tissue to speak of!!). The latest reserach shows you can improve your breast firmness by wearing the correct size, but it does take about 1 year as the coopers ligament takes this time to reattach to the pectoral muscle.
Go get fitted at a proper store where they stock from AAA to K cups and thus can fit you correctly: If they only run A-DD "amazingly" they will tell you DD as they have nothing more for you, but remember FF/G cups are average when you look at them and K cups are big.