Help!

Kirsty
So af was due on the 12th and still nothing yet, no symptoms of her coming usually get extremely irritable and moody with bad cramps and couple of days before, I got some slight cramping yesterday and again this morning, but it has gone, I feel belly feels really light. 
I usually have 30/31 day cycles and I'm on CD 39! 
When would be best day to test?