Honestly, I know it sounds mad and you can't see that it'll work, but please trust us
. In a good fitting bra you will not get lumps, overspill or back fat. Yes, the band may feel tight at first after wearing such a loose one but you will soon get used to it.
Your current band is uncomfortable because it is the wrong size and your boobs are unsupported as dragging on your band. A 36C would be excruciating on me but a 30G is very comfortable.
As mentioned a few posts ago, bra sizes given for busty celebs (eg Christina Hedricks) are wrong. The media promoted that anything above a D is 'outsize' and therefore celebs never say that they're bigger than a DD they just increase the band size and say "oh yes I'm a 36DD"! For example, I've seen a magazine saying Katie Price is a 38DD. She is tiny and is probably something like a 26GG.
A D, DD, E, F etc are not big sizes it's just we've been conditioned to think they are.
Can you post some pics? Side, front and back views would enable some of us to give you a better opinion about possible problems. Obviously, a fitting at Bravissimo or JL is the best idea. Don't discount Bravissimo, I bet they'll have bras to it you
.