Positive opk days before AF...HELP

Jeralee • Married to the love of my life for 3 years. Ttc since March 2015. Hoping our BFP comes soon!! IVF #1- BFN
I am so confused. AF is supposed to show up 4/13. I had a lot of slippery cm this afternoon so I decided to take a ovulation test since I've been getting bfns on preg tests. Then I got a very positive opk....why would this be? Am I just o ing much later than glow predicted? Help!