I'm hoping you can help me with this seemingly odd question. I am just about 23 weeks pregnant and have started to experience a strange feeling in my pelvic floor - the best way I can describe it is a vibration that lasts for about 5-10 seconds (as if someone were running a vacuum cleaner near me). I've searched the Internet and have come up with nothing. Other symptoms I've noticed are lower back pain -- similar to menstrual cramps and some pain in my side and lower abdomen.
Some babies have pronounced startle reflexes, and they shake when startled (they can startle themselves, of course), which might account for the pelvic floor sensations. Your other pains should be reported to your practitioner--they may be just due to fatigue, but they might also be a mild urinary tract infection or the like.
-- Cynthia, CNM