Early Labor Pains? Normal?

I'm 38 weeks and 1 day and last night I was having bad period like cramps they are in my back as well as my lower stomach. Now they have been coming every 30 minutes and last only 30 seconds long it has been doing this for about 2 hours now. They are not very intense but I still notice them. Is this normal pregnancy pains or start of labor? 1 1/2 cm. dialled and 50% effaced.