Is labor coming???

This is my 3rd baby. My first was a week and a half late and my second I had at 38 +5. I’m currently 33 weeks. Baby is already 5 lbs and I’m uncomfortable like crazy. I can not imagine going full term. I can’t even walk without pressure and pain in my stomach area and my feet and back are killing me. My discharge is weird now and I thought I experienced all pregnancy symptoms from previous pregnancies but I guess not. How did you know when labor was impending for you with your third??? I have a drs appointment tomorrow and hope she gives me a answer because I’m in pain majority of the day