TMI Diarrhea at 30 weeks pregnant.

Madison • My name is Madison! I am due December 5th!
I'm 30 weeks pregnant and for the last week I have had off and on diarrhea. Right before I get stomach cramps, but other than that I feel fine. I had it 3 days in a row then went two days without anything and then today it is back. I have heard it is a sign of preterm labor, but I'm not experiencing any other symptoms. Have any you ever been through this or know if this is common or not?