it can just be lighting which is the baby moving into position for birth. But if you have a lot of pelvic pressure between your anus and vagina with contractions you should call. because you can also be going into early labor and if so if you catch in time you can get medication to hold the baby and steroid shots if the baby wants to come. hope this helps
Its normal. The baby is starting to drop and your pelvis is steching and getting ready to deliver. Also your baby is gaining most of its weight now and as you know your stomach is getting tighter. Try not to sit with your legs closed as spreading them slighlty can releave some of that pressure. Also if the pain is uncomfortable at night Tylenol PM works good. If you still can't get comfortable let your doctor know they can usually give you somthing to help.