BFP and a Bridesmaid in Sept 😦

hey guys.. I'm having an internal struggle here. one of my best friends asked me to be a bridesmaid a few months ago for her wedding in September and I just found out yesterday that I'm pregnant and due Nov 9.. we've already gone to try on dresses and we have to place our order within the next three weeks!! I don't know what to do. I don't want to tell anyone about the pregnancy so soon but in this situation I feel like I have no choice. I want to be in her wedding but just don't see how because there's no way I'm gonna fit in that dress at 7 months pregnant. what do you guys think I should do?