I postponed buying a bra for a long time (resulting in my first size being 75C - 34C in the US). What mostly helped me was to buy a bra that was slightly too large band-size-y, so it didn't fit as snugly and I felt I could still breathe.

Also, a good bra will actually protect your breasts from sensations. A bra doesn't move - a top or a tshirt will. The "padding" (even in non-padded bras) will ensure you'll actually feel less once you get used to it.