I'm so sorry you don't like it!! But I expect you're just being self-critical, I'm sure you're gorgeous in it!!!
If you're feeling like it makes you hunchy, remember that you're there, trying it on, pins, florescent lighting, etc. It could just be situational. If it's more than that, you might try a ballet class or some yoga - they go a long way toward getting you more upright.
But I'm still 100% sure you're gorgeous in it!!!