My one and only brother is finally getting married at the end of the month. And I need some help finding a dress.

Here are the facts:
I will be about 8 to 9 weeks pregnant.
I haven't told my family yet because we are being cautious after a previous loss.
I do have a toddler who is the flower girl.
There's a potential I might be carrying more than one (IUI, extremely high beta, will find out next week)

I bought a regular dress before I found I was pregnant. I wore spanx.

Question:
1)do you think I should look for a maternity dress? I know some people show early (2nd pregnancy, etc).
2)OR should I just wear the dress I bought...and hope that it still fits?