I am trying so hard to lose weight and tried everything I could think of but haven't. Any suggestions?

I am a mother of four and I have gained alot of weight since the birth of my first child. I want to lose at least 60-65 pounds before the end of the year. I tried weight watchers, slim fast, atkins, south beach and my own diets. I just want to lose the weight in a healthly way.I am a 28 year old woman who don't want to blame having kids for being overweight. I don't have money for Jenny Craig and all those other places that charge for the meal.The man who I am marrying says he loves me the way I am but I want to be healthy and when we do get married I don't want to look like a blimp in the pictures. I welcome any suggestions.