I had it as early as 6 weeks pregnant and they say it's not meant to start till the 2nd trimester. i put it down to me being quite tiny and my ligaments and uterus is having to stretch quite early to accomodate a baby .... when i have it its like a sharp pain for a split second and then it goes away... happens alot when i cough and sneeze or just turn the wrong way in bed too quickly....
i would get it checked out if it seems to be lingering a little longer... your insides are getting shoved all around so it could just be some other body part in an uncomfortable position.... seeing a doctor isn't going to hurt... will only put your mind to rest.