The general rule is 4-1-1. Contractions 4 minutes apart lasting 1 minute for 1 hour is when it's time to go to labor. A lot of people don't lose their mucus plug and most people actually have their water broken by their doctor. Contractions aren't painful for everyone. My water broke on its own and I didn't even feel tightenings, but contractions were coming up on the monitor.
I would call your doctor you could definitely be in labor. I barely felt my contractions and mostly had tightening with my two previous pregnancies to go to the hospital to find out I was 5 cm dialated. I never lost my mucus plug with either and both times the doctor broke my water. With them getting closer together I would get it checked out! Good luck :)