No need to panic.
Just follow the book, and do alternating days of pp and pv. You'll get the hang of it very quickly.
If you get a tiny bump on the scales, ignore it.
It's not fat - it's just a bit of water, as your body settles with a sigh into the new routine.
Later, when you feel more secure, you can experiment with different combinations of pp and pv days, to suit your lifestyle.