It sounds like things are progressing normally for you. Congrats on day 4!
And remember, you haven't been putting much into your system, so "real" BMs might not resume until after the fast and you're getting solid food.
The headaches should completely clear up soon, but you can expect the bizarre vivid dreams to recur (I love those!).
I'm glad you're back to your surly self, I get in the happiest most positive mood during my cleanses and I can't stand it sometimes! Dagnabbit, I'm a sardonic pessimistic angry belligerent misanthrope! Sadly, such is not the case during the MC, and then it can take many weeks to return my old sarcastic sharp-tongued self. Alas, the things I endure for a little detoxing.