It's probably just pressure from the baby's head bearing down as your body is preparing for labor in the next few weeks. Are you having contractions or just the pressure? The closer to your due date you get, the more pressure you will experience as baby drops and gets into position.
I started feeling that way the night before I went into labor. I didn't have any labor pains, only a lower back ache and I had to go to the bathroom. Then the labor kicked in hard and I had to go to the bathroom several times. When I got to the hospital a couple of hours later, I was 6cm dialated. Good luck
Make sure you are resting and drinking plenty of water. Baby is getting bigger and may be laying in a position that is causing the discomfort. Contractions will get more regular and harder when you are in labor.