cramps in 3rd trimester

Susan • 25. Married to a soldier. Expecting our first. New Yorker at heart. Healthcare is my passion.
I'll be 36 weeks tomorrow and the last few days I've had consistent cramping all day long. At my doctors appointment this morning I did mention it to my doctor and she said it's normal but didn't elaborate on it. Just curious if anyone knows WHY this happens? I've read it can be the cervix thinning and the body preparing for labor? Looking for someone that might actually know a true answer..