Big Boobs are so overrated

I think I'd rather be pregnant again right now. Went back to the gym for the first time in over a year last night... it wasn't pretty. It started out good - walking on the treadmill at a good pace listening to good music. Then I tried to jog... it got ugly... not only was I completely winded almost right away (I imagine my face was beat red too) but I might as well have been wearing nothing for all the support and control my sports bra was providing to my out of control boobage. Ridiculous I tell you. So I'm trying to run while inconspicuously holding my boobs so they don't flop all over the place. Maybe it didn't look as bad as it felt - but if I wasn't holding them down it felt like they were going to detach. They're looking pretty baggy saggy as it is - I don't need to further destroy them and make them even more saggy by running. Since 99% of my life I've had a B cup or smaller I'm at a loss as to how to deal. Any tips?

(BTW - the sports bra I bought is brand new and is fitted for my current endowment which is the D-DD range).

So I can now add working out difficulties to my list of why big boobs suck. Also on that list is boob sweat (ew so gross why didn't anybody ever tell me about this??), none of my shirts fit, self concious about looking like a hussy b/c I'm showing too much clevage, they bounce everywhere, and guys don't look you in the eye (I had heard about this but with having a B size usually didn't experience it).