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!
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.
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