Wedding dress is way too small

Can I please have some advice? Am I in the wrong in any way?
Last year in march I travelled hours to a wedding dress shop where they sold my dream wedding dresses, all went okay, I chose my dress and wanted to order it. When it came to ordering it, the lady didn’t even take my measurements and just said the sample fit me fine. Obviously she’s a reputable wedding dress shop with loads of 5/5 star reviews, I don’t know any better so that was that and we paid the deposit which was more than half of the dress (I don’t know if that’s normal)
3 months later I was asked to pay the outstanding balance, which to be fair was agreed when I ordered the dress but when speaking to other people, apparently this isn’t normal practice and normally the outstanding balance is paid upon first fitting of your dress arriving to shop. I honestly didn’t mind paying it when she asked but there was a lot of chasing from that point about when my dress would arrive in the store. I was told it would be the start of jan, which came around and it wasn’t there, chased again and anyway, the dress didn’t arrive until the march (4 months before my wedding) When it came to collecting the dress, baring in mind I had to do a round trip of 5 hours, she asked me when I could come. I asked her for a Saturday which she said they are far too busy (that’s completely understandable) and asked me to come on a week day. Arranged this with my mum and step dad, who took time off work to come with me, for her to message me and say that can I now come on Saturday as brides have moved around there appointments? And gave me a time slot for if I wanted to just collect and a different time slot to actually try the dress on. I replied and said I wouldn’t be able to do that as my mum and step dad took time off work and anyway she said okay that’s fine just stick to the collection day I had before. When it came to collecting the dress, tried the dress on, it wouldn’t zip up. As soon as she realised this, she asked me if I had put on weight (I haven’t, as I have been weighing myself basically since I’ve been planning my wedding). I actually stood there in the shop and just wanted to cry as I just had enough. The dress was A LOT of money, paid in full 8 months before, took basically a year to arrive to the shop and I had 4 months to go. She convinced me that it would do up with someone strong enough to do it and that was that, I just wanted the dress of me. Came back home, and needed to get the straps and length altered so took it to a seamstress straight away as basically everyone near me was fully booked until September.Went with my mother in law, who when I tried the dress on told me it wouldn’t zip up by a long way. Like even if I lost a few pounds it wouldn’t do up. Seamstress said it’s fine, she’ll add in a bit of material and have corset back. Roll round to today, message off her saying she doesn’t want to do it, she doesn’t know how it will work because of placement of straps etc the dress is too intricate. So I message the bridal shop, not that they can do anything 11 weeks before my wedding and she just said straight away they have the same dress coming in a bigger size next week and I could swap. Sent me the measurements of the bigger size and asked me for mine. I took my measurements and even the bigger size is way off my measurements! So yeah, I’m up all night stressing and panicking. Hopefully can find a seamstress who can do it, if it will even be done. Upon speaking to another bridal shop, they told me that regardless of if I sample dress fit (especially a dress like mine which has a structured, boning top section) measurements should always be took because the sample dress will be a lot more worn and fit looser, where as the new dress will have no give. Just needed a rant and a bit of advice really, am I wrong for thinking the bridal shop is in the wrong? I’m so upset and my experience has been so bad