I do the same kind of workouts. If I feel off, I do yoga. If I have severe cramps I lie on the sofa moaning in foetal position instead.
Losing that much weight in four days is ridiculous. Try four months instead. And that might even be a too short time.
If you want to change your body, start now even though it won't happen in four days. Six months working for the body you want are six months well spent that make you never have to want to lose large amounts of weight in just a few days again. The healthier and slower you do it, the bigger chance you stay that way and it never ever comes back again.