Same here!
I wear a 40/42 DDD..sometimes an F if it's a custom fit bra and I really don't want to lose them. They're kind of what I'm famous for around here..

Guys stare at boobs regardless, but I've had straight women stare at them too and actually come up to me on the street and compliment them

which I can't lie, was an ego boost.
My mother in-law's boss (who is in her 80s) actually complimented my husband on them.


Needless to say, he didn't really know what to say. And I've never had an issue with back pain.
I expect to go down several cup sizes as I lose the weight, but I'd like to keep right at a D/DD cup. I think I was a 38 C at my skinniest and even then I don't think I was wearing the correct size.
They're actually still kind of perky (as perky as a DDD can be) and I rarely have to wear a push-up bra. I guess it comes from rarely not wearing some type of support, which is a trick I learned from my mother. She told me when I was a teenager to always sleep in a comfortable bra (obviously not a high quality one). She said it wouldn't stop time and gravity forever, but would delay the time before they start to sag with age.