Christ on a crutch! That's an awful lot to be losing on a monthly basis, love! I'll not say it won't work, because perhaps your metabolism just is very different to mine. Until recently, I'd been successfully averaging a loss of 2lb a week since January 7th - I'm presently on a bit of a plateau.
I would say that it's a good idea to set your target something that you are ABSOLUTELY CONFIDENT you can reach, and expect that you can probably beat. And then over and above that target, you can set yourself a challenge to aim for. Because even if you've set yourself a modest goal, like one pound per week, or, ****, half a pound per week, the buzz you get from successfully meeting and beating that target keeps you motivated, and THAT keeps you on track. Whereas if you set yourself unrealistic targets, then even though you HAVE been making progress you'll feel disheartened, and thus be that much more likely to give up.
I found it TREMENDOUSLY encouraging to make myself a little graph plotting how my weight would change if I consistently lost a pound a week. I pencilled in where I would be each week as my goal, and then took GREAT delight in colouring in where I ACTUALLY got to each week - because of course I was doing a lot better than that. And then as and when you hit plateaus, you still feel good because you're already ahead of the game - and that helps you to keep motivated.
Generally, my understanding was that a healthy rate of weightloss was between one and two pounds per week. And whilst I certainly understand the desire to just get rid of the fat asap, the key thing here is to be able to stick with the program for the long haul - because once you've shifted the fat, you STILL need to stay on plan and not go back to old habits. So losing gradually isn't such a bad thing, really.