Hi, I just posted a
blog post about bra buying tips while losing weight.
The biggest thing, though, is to remember that your underbust=band size (and measure tightly!!). Whatever you do DON'T add inches, otherwise you really could get quite a bit of back pain!! Also, make sure the center gore is flat against your chest and that your breasts are completely enclosed in the cups (basically no quadraboob or underarm fat!).
If you need help with fitting you can post your measurements here and I can suggest a size to start with (But nothing beats trying on bras in person) and also check out my
bra fitting page for more help.
BTW, you DON'T need to spend $100 on a well-fitting bra. Check out places like brastop and ebay UK (They have international shipping and brastop sometimes has FREE international shipping and the prices are a lot lower!). Also, Ewa Michalak bras are very affordable and the shipping isn't too bad and those are probably the highest quality bras that I have ever seen!