Uncomfortable Braxton Hicks or Preterm labor?

Hello ladies I'm 28+5 weeks with Di/Di Twin Girls and since lastnight I've been having what I believe is Braxton Hicks but they are starting to be uncomfortable and I have been experiencing lots of back pain with them it's been every 3 minutes that they come and go, should I be worried? I've been drinking water and tried sleeping on my left side and they still come! Just looking for any words of wisdom here before I call and bug the nurses