Call your doctor since you're that far along. But in the meantime Put a pad on and if you keep getting it wet it's most likely your water. If the bag breaks near the top you'll get a slow continuous trickle. When the bag breaks down low or near the birth canal is where you get a gush of water. Also, you could try smelling it...it could be sweet/odorless.
I was in bed at 6am it was just a little so I thought it was discharge and I worked all day til 5:30 with it leaking a little during the day went to labor and delivery after work and they told me it was my water