I'm 29 weeks with di/di twin boys. I'm scared of having preterm labour and not to understand the symptoms. It's been two days i feel my belly very heavy, i have discharge much more than before, i have contractions that can last 1 hour every 10 minutes then they stop for a couple of hours. Now i have lower back pain and some mild cramping. Is this all normal or these are symptoms that i have to see the doctor?