Stick with it... It gets easier, ime. I did the c25k too, and dreaded each week change, but even I made it through to the end, and for a few months I even went back to the start and did the intervals with slow run/fast run instead of walk/jog.

Following the bra question: I'm a 12G, and also struggle to find one that fits, let alone allows me to run. I was using 2 sports bras, one on top of the other. Part if my problem is that to get any kind if support it needs to be quite firm around my ribs, and that in turn limits my breathing. :/