I don't really care for the Biggest loser. On this board we aren't in competition for "money" to see how much someone can lose in a certain amount of time. It's unrealistic. After all it doesn't account for the daily hoops that the average person jumps through during the day--juggling jobs/school and kids.
Here is a great site for you to determine where you are so you can start--and on the same site that tells you how many calories you should consume to get to your goal weight.
They recommend (for long term weight loss success) losing one to two pounds a week.
Judging from your tremendous weight loss two times in the past, you probably went on a pretty severe form of weird diet--only to eat a piece of bread and gain it all back--plus some.
It's time to get realistic with yourself--change some habits--and think of this as a lifetime of weight control without the word "diet" in it. IOW--a lot of times people confuse--calories with eating food that is considered bad. A calorie is a calorie no matter how you get it.
That's very important to remember.
A sugar cookie is loaded with empty calories--where an apple is loaded with healthy calories and carbs. Protein and carbs in the right amount and right way will not only help you lose weight--but it will help you to keep it off.
Make a plan--be realistic--commit yourself to a Permanent life-style change of not only watching what you're eating but how much you're eating. Eat less move more--is the key.
It's not rocket science--calories consumed in a day versus calories burned in a day. If you can invest in a Fitbit or Jawbone UP that will sync with a great free app on your smart phone and or computer called myfitnesspal that makes it very easy to keep track of the calories your consuming in a day, and the other device will determine the steps you take in a day--giving an accurate account of your calories consumed versus calories burned.
Welcome and Good luck to you!