this exact same thing happened to me. On my first shopping trip, my big sister travelled 3 hours from Hull, my little sister drove 2 hours from Southampton... we all went shopping... and the whole experience was completely underwhelming, I tried on about 18 dresses and found one that was ok, but nothing special. So my sisters came all that way for nothing as I didnt buy anything!
I resigned myself to the fact that I was never going to find a dress I really loved.
My second trip was a little more successful as I was starting to get a better idea for what shape dress I liked... I thought I'd found the one, but again, thought it was nice, but wasnt blown over by it.
FINALLY I found a Maggie Sottero gown online called Jenna. I called a local shop who ordered in a sample dress for me... I tried it on and almost cried with relief! BUT still, my mum didnt cry or anything like that. It's stressful finding a dress and I didnt like it either because it was all so disappointing.
My advice would be, if you're getting fed up of it to stop for a while - and if you're not sure about either dress, then keep looking and remember what you like about each dress - the shape, colour etc so you can piece together an idea for your perfect dress in your head :)
GOOD LUCK AND DON'T PANIC!!!! You'll find it :) xxx