Well the midwife has referred me to the physio. When she was taking the fundal height she was obviously pressing down on my pubic bone which was really quite tender, and I was so sore lying on my back on the couch. She said it'd probably get better as the baby rises out of my pelvis a bit more, then worse again as it grows and gets heavier!! Eek!!
The only advice she gave was to sleep with a small pillow between my knees which I'd been trying to do. And also not to cross my legs in any way, even crossing the ankles.
On the plus side one of the nurses at work gave me a v shaped pillow which I had been sitting on yesterday (the open part of the v to the back) and it worked wonders. Think I might invest in a proper cushion like yours though Toon!!