I'm in the middle of my fertile window & have been having sex every second day for the last week. On the 16th Feb I started getting lower abdominal cramps, similar to pre period cramping but much less painful, I've had them on & off for 5 days now. It doesn't feel like what ovulation cramps are described as & it's completely different to my usual monthly cramps, I've never had cramps last this long without bleeding before. Has anyone experienced this & can provide some light on what it could be?