no LH surge yet Day 17

My wife usually ovulates day 14, sometimes day 15 of her cycle. We inseminated day 15 and 16, and now it's day 17 and she still has not had an LH surge. She had a full period last month, So I am positive there's no chance she's pregnant (though we both wish it were so!). She recently started going back to the gym and eating healthier to maintain a hospitable environment for a baby. Have any of you experienced a delay in ovulation after a diet/exercise change? The weirdest part of this was, her period was 4 days late-- and she is never late. So we had false hope last month and were heartbroken when the pregnancy tests were negative and her period showed up. But now we are wondering what's going on with her cycle. Any input, ladies?