kta - it's available at REI or you can order it online.
It could one of two things I think - some sort of stomach bug as Val mentioned or a partial obstruction. Is the cramping on a regular schedule? If so, that could indicate a partial obstruction. It's paristalsis and the cramping comes in waves.
If you start getting light-headed or start vomiting, take yourself to the ER. Try to keep yourself very hydrated if possible. You can make your own rehydration solution if you can't get out or you don't want to wait for something you order.
Here's a simple recipe:
sugar (table sugar): 8 level teaspoons (40 ml/40 g)
salt (table salt): 1 level teaspoon
clean drinking water: 1 liter).
Fructose (fruit sugar) or artificial sweeteners should not be substituted for the table sugar.
To add add potassium and to improve taste, you may add orange juice or banana. To each liter, add: A half cup of orange juice or
half of a mashed banana
If the diarrhea is not too severe, a reduced concentration oral rehydration solution may be preferred - but beware of salt loss if you're not getting replacement sodium from elsewhere.
kathy