Hi Miss Ruby!
I wish I had answers for you as well. With your history of gaining and losing effortlessly, it sounds like a metabolic issue. I have tried dozens of diets, what works for me now is called the Carbohydrates Addict Diet. You can Google that, there is a test on that site to see if you are "addicted" to carbs. And, what that really means is, does your body produce too much insulin when you eat carb-rich foods. If it does, then the excessive insulin will make your brain think you need to eat more, hence, never satisfied and always hungry and craving carbs.
I believe it is a very doable lifestyle. You can have a reward meal everyday, which includes desserts, if you want. You will have to eat that meal within the hour as to not trigger the insulin "dump" that starts the cycle over again. I just started back on this on Dec 9th, lost about 10 pounds since that time. The best thing is, I am not hungry between meals.
Best wishes to you!
Jodi