Not doing the SWF (Salt-Water-Flush) and not having bowel movemnts is why you felt so sick.
Yes, it's the toxins. But it doesn't help that you didn't flush the toxins out of your colon.
caffeine headaches and withdrawl sucks. Been there. It's easier to get off caffeine before doing the fast. But fasting is kinda pointless if you're going to get dependent on it all over again.