I've got a sow due to farrow in about 3 weeks - appears perfectly healthy, eating well, drinking well etc....but has suddenly started to eat her own faeces!!!!!

As a consequence, she's now a bit 'squitty' and is trying to eat that too. Because of the lack of rain, the paddocks are very dry and bare, but she does have a long strip of greenery that she can access as I moved the electric fence...but I'm not sure she's eating it

I rush out there and try and pick it up before she does, but I can't be watching her all the time. She's never done this before and I can't find anything on the Pig Websites about this 'condition'. Anyone any ideas please???
Thanks all.