I think it may be unrealistic to try to lose 100 pounds in the next several months without putting yourself at risk unless you are doing it under close supervision. It may be a better strategy to go more slowly.
Check out www.whoatemyblog.com - it's a really interesting blog by a guy who I have gotten to know through Twitter - he has lost a significant amount of weight over the past couple of years, and documents his struggles and successes in a very open way.
I have done the HCG diet in the past with much success. I got married in September and a few months prior decided to start dieting for the wedding. With not much time, and a lot of weight to lose, I did the HCG diet. I lost about 30 pounds over a trial of 2 months. I wasn't great at following the diet word for word or I'm sure I would have lost more weight. I am now trying the diet again after gaining some weight back because I was eating fast food for lunch everyday. Good Luck!
Try drinking 2 glasses of water before and after meal. This not promise you a fast result but it can really help you. Try doing this associated with proper exercise and that i assure you that good result.