lower abdominal pain

Hey everyone so I'm sixth months pregnant and have been noticing some really sharp pain in my lower abdominal area after urinating! Not sure if it's gas or my uterus just stretching? I had gas right after urinating and I feel a little better. I have an appointment on the 6th of January so I can as my ob then, I'm out of town right now so only thing I can do is call and ask?