I'm due Oct 2nd, am currently 36 weeks & my baby dropped at 34 weeks causing lots of pressure in my pelvis & bottom. It's really very uncomfortable. Sometimes I lay on the couch, put pillows under my hips to get him out of my pelvis for a while. We're in the home stretch!
I remember reading that when you feel a pressure on the bottom of your stomach that means that your baby has dropped and is trying to get into the right position for birth. Sometimes it'll take awhile before he/she comes tho. If you start feeling any sort of pain and if it's in your back as well and comes and goes I would def talk to your doctor.