White dress options?

We’re having a long awaited wedding celebration in May and with any luck I’ll be pregnant by then (fingers crossed for a positive in a few days) so my original wedding dress likely won’t fit if I am pregnant. I don’t need another “wedding” dress per se but something white would be good. Knee length to ankle length. I currently wear an XL in most things, size 16/18. 5’4” and 210 lbs. If I do end up being pregnant, where should I look for dresses? Easy returns necessary as things don’t always fit as advertised. Thanks!