Welcome
I'm so glad you joined here. You can do this! Although I haven't tried it myself, I hear good things about Weight Watchers. My good friend and neighbor lost 60 lbs on WW, slowly and steadily. It took some time, like any healthy weight loss, but she has kept it off for 2 years. She's an inspiration to me.
I also have set 100 lbs as my dream weight loss goal. I don't set goals of every 10 lbs... I set them for every 5 lbs., lol! I don't want to get discouraged, and personally I seem to do better with mini-goals. I have been amazed at the innovative ideas 3FC members have come up with to track progress and keep themselves motivated, from moving marbles over from one jar to another, to thinking of weight lost in sticks of butter.
We are here for you, and good luck!