Hi, back again...I'm now 32.5 weeks, and feeling quite large, as do boobs! I would like to say though, tyhe books and shops and midwives all say you should get a maternity bra from about 4 months onwards, which I didn't (partly due to money, and partly because they were ugly and partly because of ignorance..)
I have since bought myself a couple, and regardless of how big or small you all feel, they are very very comfortable....but do suggest you get fitted. Saying that, I got fitted in myer in the city, and thought they did a terrible job, and that they were terribly pushy. If you aren't sure if you are comfy, or have been given the right size, don't be pushed into buying one. I went to a couple of different shops to get fitted and ultimaely ended up at myers in a different suburb, where i received superb service and finally made my purchase.
Thought I'd mention this, because I didn't notice my boobs getting that much bigger as was too busy admiring my belly growing. My hubby kept telling me i had big boobies, but didn't pay any attention until i got the tape measure out....so girls, don't forget about your other growing assets!
PS The bigger the shop, the better selection of maternity bras they have (and prettier colours). Also, Myers have 30% off of all undies at the mo....
...Being a teenager might put you off a maternity bra as they are rather industrial, but do have a look though, there really are some pretty ones out there! Good luck.