4th day of fertile window!

Ok so I am on my fourth green fertile day. I BD the first day and today is 27% so I am BD today and tomorrow which will be 33%. Then off one day and once more this Sunday but I am feeling very crampy today is that due to ovulation? I have been focusing on my body a lot lately and I have never noticed getting this bad of cramps near ovulation. It almost feels like period cramps. Please share inputs I would like to hear if this has happened to anyone else. Thanks in advance.