Mine only got a tiny bit bigger as well and im 40 weeks today (fml lol) i went from a 36C to a 40C and thats pretty much just because the top of my stomach got so much bigger that i had to get a bigger size around but not really much of a change in cup size...theyre starting to get a little bit bigger now though...but im guessing thats cuz my milk is going to come in within the next week lol if this little boy would show up already!
Not everyone will have increased breast size, especially those who have had previous pregnancies. Once your milk comes in I would be prepared for them to get bigger, atleast for a little while. The last couple of pregnancies I've had mine don't get any bigger. They feel fuller or firmer I guess you could say but no increase in bra size.
did they grow during the beginning of your preg? i recall with my son my boobs didnt grow much at all...however this one i start an A cup and im pushing a DD now...its amazing how dramatic my boobs have changed
just remember that everybody is different and im sure everything is ok...you are almost full term....so exciting :)