11 days late????

Kayla • I`m 24 old! I`m married to the father of my son and have been for 3.5 years! My sons name is Zachary!Ttc 2 years
So I am 11 days late today I took a test yesterday and it was negative.. What is going on.. I'm always regular 28-30 day cycle and today is day 40 of my cycle.. Could I still be Prego even though the test yesterday says -