when does a hug become a bad thing? probably when you've eaten a whole bag in a day and a half

I have always been considered small framed. Growing up I was painfully thin. I didn't hit 100 pounds until I was a senior in high school. Because of being thin growing up, I began to worry about gaining weight. The majority of women in my family start out thin and gain weight with age. I do have a few women in my family who are larger than others. I began noticing the different sizes of my aunts and cousins and also began to worry. I was one of those, I can eat whatever I want kind of people, knowing I would still be thin. I never worked out. I was always curious about my weight and became a little obsessive about it.
Since I graduated from high school 16 years ago, I have gained about 30 pounds. The first year Drew and I were together I gained 20 of those 30. I knew I was getting bigger and thought nothing of it. My mom popped that bubble when the day before my wedding she told me I had gained weight. Since then my weight has gone up and down (I have gotten very good at hiding my weight). Two weeks ago I weigh myself and was shocked to see I lost 10 pounds. I really want to keep that weight off and lose another 10 pounds. My problem is I have no discipline and no self control. I go in spurts. I'll eat super monster healthy for a while, decide to reward myself and suddenly I'm of the wagon. I fell off the wagon this week and I hate it. I'm gross! I've eaten so much candy this week it's pathetic. I don't even really like candy, I eat it because it's there. Where is my self control? where is the discipline I had in my 20's? I used to kick box. I did kick boxing 4 times a week for 3 years. I was in such awesome shape. I miss those days. Since then I have broken both my ankles and ruined my knees. I don't have cartilage in my left knee, my right knee has some left and I have jacked up MCLs. Kinda makes you wonder how I walk. I manage, but I will need both knees replaced by the time I'm 40.
I want to get healthy. I want to get back into shape. I don't want to be one of those people who can't work out. I have thought about looking into Yoga or Pilaties, but money is a factor there. It's such a bummer.
I know I probably won't go back to the body I had when I was 23, but if I looked something like that, I'd be pretty darn happy.