Early signs of labor

Did you experience anything that indicated the nearness of labor? I'm feeling really unsure about how to assess the situation when it actually begins. I'm 39 weeks and experiencing some lower back pain and period-like cramps but I don't want to get excited over nothing. Was there anything that made you think "this is it" before the actual contractions started? Aside from physical symptoms, did you get a "sense" that it was about to happen beforehand or did it just come out of nowhere? I would really appreciate some insight!