First: Stop beating yourself up. Start making the right choices; poor food choices lead to cravings and more poor food choices.
You don't need weeks of training in the gym nor tons of dedication, just focus on small, reasonable steps.
Check out SP's articles on this issue, they'll help! www.sparkpeople.com/resource/nutrition_art
Here's a blog by IndyGirl, one of our most successul members! www.sparkpeople.com/blog/blog.asp?post=tip