AF less than 2 weeks after Ovulation, help please

Shari
Hi ladies,
This whole TTC business is both heartbreaking and frustrating. I was convinced this was our month but alas the wicked witch appeared this morning followed by the usual tears and heartache. 
So here I am tiring to rationalise it and find the 'issue' hoping for a little help please. I have a positive opk in Monday 11th so would expected to O on Tuesday or Wednesday but AF showed up this morning, approximately 12 days post O. I read that the late leutial phase should be no shorter than 14 days - could this be the problem??
Any advise or support would be greatly appreciated. Thank you x