Everyone's labor is different. My first two I hardly knew I was in labor. The second two I had to be induced. Your body could be getting ready for labor sometimes it starts early. There other thing is all of mine were late. Good luck
It is different for everyone. In general when the pains have a pattern, start coming regularly than it's usually the start of labor. Many women experience Braxton Hicks which are false contractions, sometimes uncomfortable sometimes just a tightening- these can be relieved by rest and staying hydrated. I always checked with my doc to make sure when I first experience them, just to be on the safe side.
I thought my contractions were braxton hicks because people told me I would "just know " when it was the real deal. They were wrong! Trust your instincts and your own body!