It's not unusual for a woman to start losing her plug early on. The thing about the mucus plug is that it can regenerate itself. I would mention it to your doctor to see if they want to possibly check for dialation but loss of the mucus plug by itself isn't really an indicator that you will go into labor anytime soon.
The plug can come out all at once or little by little over the weeks. Mine always slowly came out. I had pre-term labor last pregnancy and was dilated 4cm for over a month. The mucous plug looks like gelatin almost, it's a little different than normal discharge. I only worried when I saw it streaked with blood or when I had regular contractions.