Yes, that is normal. It is your body's way of telling you that your electrolytes are out of balance. You should eat some bananas (they're good for diarrhea anyway) and sip small amounts of fluid at frequent intervals to help with this. If you have any potassium supplements on hand, now would be a good time to take some. If the diarrhea and/or cramping continues or gets worse, please seek medical attention. Diarrhea can cause dehydration, and in turn dehydration can cause diarrhea. It becomes a vicious cycle that can be very dangerous and require i.v. fluids to resolve.
Yes cramping after diarrhea can occur! If you've been dehydrated drink plenty of fresh water but if it persists in any way consult a professional. Diarrhea is the body's way of expelling toxins. It's a good thing if you are cleansing toxins but water is absolutely essential!