WOW - 3 stones in 56 days is fantastic! Well done.
If you have struggled with weight and other diets, then I think it is quite common for those doubts to surface, and for you to question your success, especially if you have a fair amount to lose. When you find how effective Atkins is, and begin to feel the benefits, it almost seems 'too good to be true.' But it
is true, and you are proving it to the tune of 3 stones!
Look at all those positive points in your post - you have more energy; your clothes and underwear are falling off you (just watch out where you are if they actually fall down!
) clothes are looser - and with all those pounds gone there is no way that is your imagination - those clothes really are looser, because you really are getting smaller; your friends and family tell you they can see a difference because they love you - well I bet for one thing they really can see a difference, and for another that they are just so thrilled to see your success, because, loving you, they will know how much difference it can make to your life; you love your legs, which is great - so many people with weight to lose don't recognise their good points; you can do so much more around the house, and you are planning for the future when you are going to get on that cross trainer and burn off even more calories - and just think how much you willl love your legs then!!
So it is real, and you have done brilliantly so far - keep it up, keep coming here for advice - like a lot of us do, and carry on envisioning your future slim self.
In fact, I think you should repeat after me:
'I have lost 42 lbs - that is Fan-tas-tic and I am going to look even more fantastic ' 
CP