Most likely your mucous plug fell out and it could be possible that your in labor and the contractions havent hit just yet i would go to the emergency and get checked
Go to hospital and have them check u. If ur bag broke then your baby can't stay in there for much longer.
Im 39+5 too and have lots of pressure, lower back ache and the odd contraction here and there. I havent lost my plug yet though but i didnt lose that until my labour had properly started with my daughter. My water never broke and i havent had a trickle yet either. Sounds like your waters may be leaking. Ring your midwife and good luck. X