Labor

Hey I'm 31 weeks, lost some of my mucus plug at 9am at work today. Called the triage nurse and she said to monitor myself. Later at work after lunch around 2 I had this feeling of tightness around my belly and then it would go away and come back. Some one told me they were contractions so I left work and On my way to my dr. Could this be true labor, does he want to come this early?