Terrible cramps back and stomach

So last night as I was laying in bed my I had terrible cramps in my back and stomach. I know the baby was sitting very low on my bladder and wondered if that had to do with it. I actually thought I was going into labor that's how bad the pain was but I just in the hospital last week and saw my doc a week ago too they did testing and found out I was negative for a test the predicts if your going to go into labor in the next two weeks. Anyway the pain finally subsided enough for me to fall asleep and I woke up with some pains again. Long story short it was bc I'm having some bathroom issues and after some fiber cereal and coffee this morning I'm feeling better. My real question is at this close point to our expected due dates if you've never had a baby before how do you know when you're in labor??? I know that sounds like a stupid question, anyone else thinking the same thing?