Nobody means to make you feel bad, it's just that if your weight loss is unrealistic, when you weight in and realize you're not losing enough you might think you're not successful and give up, that's why it's so important to have realistic goals.
In the other hand it's not possible to say if losing 5 stones in a few months is achievable or not without first knowing your weight. If you're 40 stones (560 pounds) for example, this weight loss would be achievable as long as you do vlcd and stick to the diet 100% as well as exercise everyday. However if you are, lets say, 12 stones (168 pounds) then it's not possible.
Calculate your BMR (just google BMR calculator) plenty out there, and work out how many calories you burn in a day then take off your calories intake off your daily calories and what's left is how much you will lose in a day in calories. If you want share your weight in this forums I can do the maths for you.
You need to lose 3500 calories to lose a 1 pounds (approximately, this is NOT exact science), then multiply it by the weeks you have left and you will see how much loss you can expect.