Lower back cramps-sign of labor?

I'm 38 weeks today and have had noticeable Braxton Hicks contractions off and on for a couple weeks. Sunday night, I had them pretty strongly for a little over an hour about 7-10 minutes apart before they went away. Today, I have started having some Major back cramps/spasms and pelvic pressure. At my appointment yesterday, I was only fingertip and 20-30% effaced. Could the new back cramps be a sign of something to come or are they just because they happen?