Why is my period weird this month????

I was expecting my period July 18th and unfortunately my luck is thin with this ttc thing and AF came lunchtime the 18th just like clockwork. It was like a light/medium to start that was Thursday, all day Friday was hardly anything but few drops and then today Saturday Iiterally nothing. This is not my norm I usually bleed medium/heavy for like 4 days and then light for the 5th sometimes 6th day. I was praying for no Af this month as we did the BD quite a few times in my fertile window in hopes of a bfp. Any idea why my af is so light and seeming like it’s going to be super short????