Missed period? Confused!

Chenise
Hi, my af is now 4 days late! I am always very regular! But I thought I maybe had ovulated a week later than predicted due to very ewcm! Bfn the last couple of days.. don't know when I should do the next test! I think I might have ovulated the 18th, cramps (not like af) and very light for last few days! Any opinions?xxx