I agree with the poster before me! I am so sorry about these feelings and the disappointment that robbed you of the moment of feeling beautiful in your dress. I think it's fantastic you have set a goal you are so passionate about but you should not have to fear what your loved ones think of you on a day as special as your wedding day.
When you look in the mirror, that's you. It's always going to be you. Even if your body size changes, weight, clothing, hair, you're always going to be you. Rest assured that the man you are going to marry thinks you're beautiful in any state and I hope you can comfortably celebrate your love soon without having to worry about any of this.
Is it really your loved ones and the people watching you eat the cake or is it a little voice inside of your head picking on you? Don't let anybody make you feel that way, even if it's you doing it. Feel wonderful and beautiful all the while on your journey, even if you have to practice outside of your comfort-zone to do so. Please be careful not to get into the deadly cycle of making yourself wait to do and see the things you love based on you being a weight you're unhappy with. Just appreciate and pamper your body and know you're going a healthy direction with your weight loss.
Now, all that aside, welcome to the forum! You just took the first step to "doing something about it." You're on the road, baby! Enjoy the ride!