OMG Julie, I so get that exact same tingling feeling before a BM. I have alternating IBS, constipation and the thebig D and I go like 5 times in one day.

Neurot Doc explained the tingling as your brain signaling the bowel to start contracting to have the BM. And because I have such exaggerated sensitive nerves I feel this more than other. THere are tons of nerves in your bowel, pelvic region more than anythere else and they lie in very close proximity to each other.

Atleast thats what he told me. I try not to worry about it (esp since I have so much more to worry about) since he said its just messaging going on in my body. Plus I have had a thorough check up in that region and nothing shows up. Just oversensitive nervous system.