Been measured and used approved methods to self measure. Unfortunately I've gone down a cup size and on the left an extra half since before pregnancy but the main issue is my post baby floppy boobs and bra shape.
I used to wear a standard t-shirt or push up style. Now though, this shape makes my boob pour down into the bottom - so there's too much boob at the bottom and not enough above!
What shapes of bra - and brands - are good for floppy old post baby breasts? My new size is 30DD/32D (of course varying by brand). I used to be 30E/32DD.
You might find that you get on better with half cups are proper balconette styles - they basically don't have a top half to the cup so you don't get the empty gaping. Something like Freya patsy, Bravissimo own brand half cups, curvy kate (they do lots) might work for you.
I would say that you should try out the half cups or balconette styles bikini tops because they don't let your breasts droop down. I have had a similar problem some time back and I never found a good bra that would properly fit me. I finally switched over to a bikini top as a lingerie. Dollboxx has some nice collection of such bikini tops. You can check their website once and see if you like something that may suit your needs. Even if you are going for bras I would suggest you to go for the half cups.
Even if you've been measured etc it still sounds to me like they don't fit if boob isn't filling the whole cup? Sometimes going down a back band can help as the cups will be less wide so will cover less area.