Pregnant bridesmaid

So my husbands brother is getting married in May and I'm a bridesmaid. We ordered our dresses in September (per the bridal store's requirement since the dresses are special order). I was planning on being pregnant, and told the girl measuring me and estimated I'd be about 6 months along. She told me to order two sizes larger. Well, got my dress this past week and tried it on last night. It fits. As in there is no way in hell it will still fit when I'm 28 weeks when I'm only 13 weeks now. There are two others that are pregnant now as well, one who will be 25 weeks and only ordered one size up and another who will be 31 weeks. I don't want to bother the bride since she is in her last semester of school and working full time as well. We are freaking out!