I got those before. Its usually pressure from the baby. Does it stop u dead in ur tracks? And only last about 15-45 seconds. If so it's normal.
Can you describe what the pain is at all? Is it constant, occurs with movement, feels like a stabbing pain in the vagina? As pregnancy progresses the weight of the baby, as well as the uterus, amniotic fluid and placenta all weigh down on the lower half of your body causing pain and cramping. Unless they're regular (contractions or BH) it usually isn't cause for concern. However anything that just doesn't seem right you should always get checked out by your doctor.