I'm a 30FF so quite similar to you in size.
I don't get backpain unless I'm standing up all day, perhaps your posture isn't quite right? I know this size boobies are heavy (cup your hands underneath them, the weight is shocking!) but how you hold yourself can have a big impact on back pain.
In terms of exercise, I bought a sports bra from debenhams for £30 and it's great! I can't believe how little bounce there is. Would definitely recommend them, and they can help you with the right size if you need it.
As above, they are very heavy and aren't going to be as perky as someone with a little B cup. It's natural, that's what gravity does. Personally, I think it's much more attractive to have boobs that actually 'fall' if you know what I mean, and have a teardrop shape rather than just be two fried eggs on a chest!
For me personally, changing myself with surgery just isn't being true. I've been made this way for a reason. Breast lifts and reductions both pose a risk to future breastfeeding, and that just isn't a risk I'm willing to take. I'd rather put up with having to spend a fortune on larger cup bras than not be able to give my children the countless benefits that breastfeeding offers them. It's a choice you have to make for yourself, but I would advise at least waiting until after you've had your family before you do anything.
Now, on to your confidence. I actually love my breasts but it hasn't always been that way; a big part of feeling better about myself was to accept my breasts weren't going to get any smaller. Then I took a long hard look in the mirror and realised they actually looked nice! Sure I can't shop for bras cheaply but I think large breasts are
so feminine and womanly. Do you have a partner? I've been lucky enough to have partners who called me beautiful and my current fella said to me a couple of years ago 'you have great tits you know'
I know it shouldn't be, but knowing other people find your breasts attractive does make a difference to how you feel about them. Lastly, how many glamour models do you see with B cup? They are all in the DD-FF bracket, men like big breasts!
I hope that helps you honey, feel free to PM me if you want to talk because I've felt like you do at the moment and know how much it sucks, I hope my little story can give you hope that things can turn around and you can learn to love yourself.