I am totally with MrsJim on the Champion/Jogbra...I am a 38DD and good support is a necessity!
They do last a long time without getting all stretched out and distorted like the cheap $5 uniboob sportsbras at your local store. Soem features to look for is cups that are nicely constructed, not just uniboob lycra like your exercise pants. I like cups that are more "separated." You wnat straps that are not stretchy-this also goes for yoru regular bras. If the straps stretch at all-you are not getting the proper support, as heavy breasts will weigh them down.
You might check out plus size stores, or online stores that sell workout wear-or wear a regular bra in a "minimizing style" and wear an athletic tank top over it. (The minimizing styles usually cover more over the cleavage area, and stop a lot of the "bounce".)
Another thing is to make sure you are wearing the correct size. Most women are not...the common problems are wearing too loose a band size, and too small a cup size. If your bra is riding up in the back, then your bra is either too old and stretched out, or the band size is too large. It should be snug enough around the ribcage not to ride up. In a standing position, if your bra center (between your breasts) is gapping out away from your chest, then your cup size is probably too small. It should be up against your skin in the center, with no breast tissue popping out the top of the cups or under your armpits!
While losing weight, it is important to check your bra fit every 5-10 pounds you lose (or gain) or every clothing size you drop.
The easiest way to measure is with a soft sewing type tape measure up under your armpits-above your breasts. This is your band size-if it is an odd number, then go up to the next even number, and wear it on the tighter hooks. Measure again across the fullest part of your breasts with a bra ON.
If the measurement is:
same:AA cup
1" more-A cup
2" more-B cup
3" more-C cup
4" more-D cup
5" more-DD or E cup
6" more-DDD or F cup
I used to wear a 40D, and had a heck of a problem getting a bra to fit right and be comfortable-until I learned how to measure, and that I was actually a 38DD! Now I don't have near the trouble!
Aphil