I don't have as much to lose, but I wanted to comment because you said you're hungry a lot (I'm someone who can't keep on being hungry all the time to lose weight - eventually I crack and overeat). The slimfast drinks will not help to fill you up - they're mostly simple carbs and sugar, which doesn't help combat hunger (and can make it worse sometimes).
I'd recommend trying to eat more filling foods that are lower in calories, such as lean proteins, fruits, veggies, whole grains, etc. Maybe try to incorporate more of them into your daily meals. Those foods help with hunger a lot more than Slimfast will.
And a couple years isn't so long, if you think about it. How long did it take to put the weight on? Probably longer. A couple years could be a good deal depending on how you look at it.
And I second the "take it one step at a time" thing. Don't think about lose 150 lbs. Maybe think about losing 10 lbs 15 times. That way you just look at one increment at a time. When you lose 10, OK, now start losing 10 again just like the first time.
Good luck with everything!

There are a lot of inspirational stories here that you can find. Maybe those will help, too.