I'm 19 weeks and have been cramping (below my belly) and having low back pain off and on since 1am. I did call my on call doctor at 9 and am waiting on a call back. I don't want to be an alarmist and I've had mild pain before but not for this long. For the mean time I'm drinking lots of water and trying to take it easy!!
Re: How to tell if pain is normal!?
All multiple pregnancies at my doctor's office are connected with a preterm labor services which includes a weekly call from the same nurse, encourages regular counting of contractions, documenting pain etc. What I was taught is with menstrual type cramps/back pain is to take tylenol, rest for 1-2 hours. If it does not go away after resting while on tylenol in 2 hours I"m supposed to call.
Cramping can be something and it can be nothing so don't ever worry about calling. Drink some water, lay down and watch some TV, take a tylenol and wait for your doc to call.