Have you had an ultrasound lately to check for polyhydramnios (excess amniotic fluid). I was 23 weeks but measured 28 and was found to have too much amniotic fluid. Sometimes it can be a sign of problems in the baby, but more often than not it is just one of those things. I am now 37 weeks, but measuring 42 weeks and expected to have this little darling weeks ago, but am still waiting!!
Just ask your dr for a scan just to check!