Feeling like period is starting?

I am 39w4d and it feels like my period is starting.
I'm having what feels sorta like menstrual cramps, but it's more consistent, and not really coming on in waves, so I can't time them.
I had this a few days ago and started having contractions like 10-15 minutes apart, but they stopped.
Is this normal?
Labor coming on? 

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