Welcome! You're not alone here, and we're all pulling for you.
I want to echo what was said before about choosing one small thing to change, and sticking with that until its not as much of a struggle any more, than picking another thing, and so on.
Start with getting rid of the soda, if you want. Going straight to water may be really hard, as depending on where you live the water may not taste too good to you. I'm getting my husband off sodas, and he doesn't even realize it! I've started buying the sugar-free powdered drink mixes - lemonade, berry, etc. that you find in the kool-aid section of the grocery store. The flavors are really good, its pretty cheap, and they're very low calorie. Usually about 5 cal. per serving, instead of over 100 cal. per serving of soda. Try that for awhile, and see if it helps. You may find that you feel so much better getting enough water in your system that you are ready to tackle something else.
Whatever you choose, don't give up! You CAN do it!

I joined 3FC at the beginning of this month and the support here is invaluable.