There is no rewind button, but only forward. I think what you feel may be the rock bottom AA talks about, well consider it a time to change things. Some folks do it all at once, and others change one thing at a time.
I'm not sure how your living situation works, but if you live alone it is a lot easier to manage the kind of food in your house. Start by surrounding yourself with healthy snacks and food choices.
I did calorie counting and that worked for me...it keeps you more accountable for what you eat and you know exactly what you are putting in.
As far as physical activity goes it is always hard in the winter. Home workout videos are great if you don't have a gym.
Now write down what you do on average every day of the week. Look at the time you have and where you can exchange maybe facebooking or watching TV for some physical activity. Set it as a priority and do something, even walking.
I know how easy it is to make excuses and procrastinate as I am a queen at that. I know exactly how you feel as far as starting. You think about it alllll the time, the more you think about it the worse you feel about yourself and situation.
Start a diary here on the forum logging what you do every day from how much you eat to physical activity. It helps keep yourself accountable. You will miss days, but don't quit. You will see changes if you change even a little. You can do it