WIBTA if I back out of my friend’s wedding?

I am 15 weeks pregnant with my first baby and she is due July 4th! My close friend is getting married late September 1,200 miles away. She moved a little over a year ago. In November she called and asked me if I would be a bridesmaid. I had JUST found out I was pregnant like the week prior so I said, “Tentatively yes. I just found out I’m pregnant and the baby is due in July, but I should be able to make it work.”

It’s now January, 9 months until the wedding. Things are starting to get more serious and conversations regarding hotels, dresses, etc are going on in the bridesmaids group chat. I started having second thoughts when looking at dresses and I realized I have no idea what size to order. I already have a small bump and it takes 2 months for the dress to get here, so by that time I’ll be even bigger. How will I know how that dress is going to fit me when I’m 2.5 months postpartum?

I started talking to my boyfriend about whether we would drive (16 hours each way), or fly. And we both agreed that either way is going to be very difficult with a 2.5 month old baby as first time parents. I also plan on breastfeeding. This trip would also cost us at least $1,500 and we’d only be there for 2 nights. It’s just starting to seem like the cons are really outweighing the pros. However, she is one of my best friends and I have the hardest time feeling like I’ve disappointed someone. I’m so worried she’s going to be mad at me as I know how important this is to her and how much time and money she has spent planning it. Me backing out would also make the amount of bridesmaids to groomsmen uneven.

So, would I be the asshole if I back out of her wedding?