Preterm labour scares

Cienna
at my anatomy scan my doctor seemed concerened about my size and my sons size and said to not stress but be prepared as there may be high risk of preterm 
labor. (of course i stressed that i'm a teen ftm) 
I'm 28w 6days today and for the past two days (and 1 am this morning) i've been having terrible bracton hicks to the point where i'm bent over in pain with shortness of breath and they last 30-90 seconds long. they usually happen three times within an hour then slow down for a few hours and come back. I dont know the difference between comtractions and BH so i never know when to call my doctor.. has anyone had this problem and actually carried to full term? i'm so worried about him coming too early.. any input helps!