i felt the same thing- i am in my 21st week of pregnancy. It was not super painful, but rather annoying. It was only on my left side, just inside of lower left hip bone. I called the doc and they said that I shouldn't worry about it unless i have bleeding and/or cramping as well. Many of my other friends experienced the EXACT pain and their doctors said they hear it all the time and its normal. It should stop shortly. Also, the more small your body frame is, the more common it is to feel pains as your organs move around to make space for the baby.
Some advice the doc gave me (just to be safe) is to drink lots of cranberry juice for a day or two in case it is a bladder infection. Also, you can stop by your doc and drop off a urine sample to be checked out.