Unexpected Short period.

Trae
So AF was due 9/19 but came on 9/18. My DH And I BD'd every other day during my fertile window multiple times. AF normally lasts between 5-7 days and comes regularly each month. Well I noticed that AF stopped completely on 9/19 and started spotting very lightly again today. I have no clue what's going on.. Has this happened to any of you before?