Hhmm... With my last 3 pregnancies, I had early labor for about 3 weeks before I actually hit active labor. 3 weeks of contractions waking me up Every Single night~ but then they'd peter out by morning. It was Extremely frustrating. The only thing that kept me going at that point was remembering that getting early labor stuff out of the way Before hitting active labor would shorten my labor considerably.
Once I was "really" in labor though, I knew by having diarrhea, starting to lose my mucus plug, and an "inward" awareness of my body. With my last labor though, I honestly didn't realize I was in labor At All until I got very serious during contractions (contractions were all over the place~ never time-able or progressed normally). By the time we got to the hospital, I was 9.5 cms.... but still didn't give birth for 4 hrs. It just didn't feel like transition~ I was still talking and acting normal.
This is your 3rd? For me, and a lot of other lots-of-kids moms I know, the 3rd, 6th, and 9th labors were very odd. It's going to be hard to know how this one will go...