Hi ooooops Congratulations on both the pregnancy and wedding :-)
I'm in the exact same situation. We are getting married in a week and a half...eek! I chose my dress a few weeks ago and it's a maxi, fairly loose flowing dress. I just didn't know how big I'd be - I'll be 14 weeks then too.
At the moment, I just look like I've eaten a big meal and can no longer do up my jeans properly, so am wearing them with a belt done up and the buttons undone.
I don't think I'd get into a tight dress without it showing, but as everyone is saying, it's so different for everyone.
It sounds as if, at your height and size, you might be ok. I am shorter at 5'2" and I think they say the taller you are, the more room you have in there for the baby to go upwards before it goes outwards, iwswim.
The main thing is that you feel comfortable and beautiful on your big day so you can really enjoy it.