Ordering bridesmaid dress TTC

Hi all. My husband and I are TTC. I am a maid of honor in my sister's wedding in December. She is having the bridal party order our dresses tomorrow from the website Azazie. We all have to order within 24 hours from our group showroom so the dresses get put in the same color dye batch. There are many dresses to choose from (even maternity) she just wants them to be the same color and long. I wish I could order when it gets closer 🙁but I don't want my dress to be a different shade then the rest of the girls.

I'm feeling a bit stuck as I really hope I'm pregnant for it. Not really sure what size to order. Should I get a dress in my current size as I don't know if I will be pregnant? Or go a couple sizes up in hopes that I will get my BFP this month or soon? Then if I'm not I would then get alterations. If I get my BFP this month I'd be 26 weeks at her wedding. Or another option is getting two dresses- one normal and a bit bigger? The website we are ordering from is very reasonable so although not ideal, I’d be willing to order two.

What are your thoughts? Anyone been in the same boat? Thanks in advance!