First and foremost, measure properly and accurately.
Bra size is the measurement around your diaphragm UNDER your breasts. Then measure around your breasts at the nipple. For each one inch difference between the two measurements add a cup size with A as Ground Zero.

SO: 38 around diaphragm and 42 around breasts = 38 DD

Then go and try on a few. Playtex 18 hour with wide straps support the weight comfortably but each one fits slightly differently. They have front closing bras.

Also try Silhouettes on-line. They have bras up to 52 DDDD and front closing ones. A very flexible return policy makes it easy to find the right fit. Buy one size and cup up and down, try them on and return what doesn't fit. They also carry colors vs. industrial white only in Macy's etc.

I too hate my bra but with gravity and age ...SIGH.