Good luck for the 3rd Harriet - you've come to the right place. Minimins is such a great site and everyone is so supportive, and know what you're going through because they are too!
Just to reiterate what has been said in previous posts - keep on glugging away at the water. I started on 2.5 litres and struggled to get that down. Up until last week I was around 3.5 - 4 litres, I then upped it to 5 litres and dropped 5lb this week (quite unusual for me) so I'm well chuffed. So get that water down you and the pounds will just melt away!