Regardless of how you got to that size, what matters now is that you have your game plan for getting back into shape and I wish you all the luck with that. You have already received so much great advice here, but if I could add just one more thing. Make sure that you are changing your eating habits for the better starting now. If you just focus on reaching your fitness goals without changing your lifestyle in the long term you might fall back to your unhealthier habits and undo all of your hard work. It's important to make those changes now at the beginning so that you experience lasting results.