First off, Mama-- get yourself a packet of earplugs. They will take that rattly edge off the crying--you know, the one designed to get a response from us.:)
Colic is usually caused by the immature nervous system developing and "coming on-line"; some babies need more stimulation and cry to stimulate themselves, and some are overstimulated, which results in their continuing to cry. This article from the University of Michigan is thorough and informative:
http://www.med.umich.edu/yourchild/topics/colic.htm
A couple of things: if you are looking for a remedy for an upset tummy,the product you want is "Gripe Water", and can often be obtained at health food stores and lactation clinics. This water also has the correct proportions of the spices used, and if you follow the directions on the box, it will not have an ill effect on the child.
Second; research in Europe has shown very promising results in regard to treating colic with a series of pediatric chiropractic treatments. Another great article:
http://www.colichelp.com/colic-chiropractic.html
Just as adults can get 'stuck' and need adjustments to re-align the spine and bones, babies can suffer from this too. Birth and being squeezed tightly in a teeny womb for the months before birth can make it so that the body is not working optimally, and colic is one result of this. We have been taking our son to a pediatric chiro/craniosacral therapist since he was 2 weeks old (my husband and his mom have a slight scoliosis, so we are doing this as a preventative measure). My son is 3 and a half now, and we have seen no ill effect after any of the many treatments he's had.
For what it's worth, the medical community used to tell parents that colic was just a phase and send them home to wait it out. Now, with the advent of Zantac and all the other GERD medications, the diagnoses has changed from 'colic' to GERD. Hypothetically, this was so moms could go home with something in hand. How hard, though, for those mothers whose children DIDN'T have GERD, but actually have run of the mill colic!
Lastly, don't be afraid to set baby in the crib and leave the room for a few minutes if you need to. Especially if you feel you might hurt your child or yourself. Some people are likely to disagree with this, however, it's my opinion that a child who is not being comforted by being held, etc. and who is crying incessantly-- well, if being held isn't working, NOT being held isn't going to hurt. Moms need to take care of themselves too!