Wedding dress question...?

Hey I'm ordering my wedding dress offline because my wedding is very soon and my dress will be here within two weeks. I measured all the parts it asked for and got the measurements for a size 10 perfectly but I'm pregnant so should I order the next size up? All measurements are at least two inches off.. I will not have a lot of time for alterations so my plan was to get the size I fit in and just get length cut off,as I don't think I will have time to alter the whole dress. I'm 12 weeks right now and will be 16 weeks when I get married. I'm not showing at all right now, but I do have a small pudge at the bottom of my stomach now, so I don't know if I will be showing at the wedding or not. Should I get the size up and try to squeeze in alterations or should I get the size that fits perfectly? Oh and my dress is made of chiffon fabric, wondering if that will stretch even a tiny bit..? Thanks for your help!