Hi, I am 4 days late for my period, I have a 30 day cycle, and this month I ovulated late in my cycle-day 20/21. So Just wondering whether the late ovualtion can cause my period to be late also. I have done a pregnancy test yesterday and it was negative, but it wasn't an early pregnancy test.

4 days is too soon for an accurate test. Tests are less than 50% accurate during the first week. Wait until about 2 weeks after your due date to take a test.