I'm 5.7 and size 10/12 before pregnancy. I'm showing for sure but i love showing it off now that i look pg and not just fat. If i was getting married now i'd wear a babydoll dress, one similar the Sara Jessica Parker wore on the red carpet when she was fully pregnant. It was white with a black ribbon under bust, very flattering.
You'll have fun shopping for the perfect dress and i bet you'll look amazing on the big day - Good Luck!

Jed