Hi, I Had Unprotected Sex On The 22nd Of May

hi, i had unprotected sex on the 22nd of may being the ovulation day since my last period was 10th may and took postinor 2 10 hrs later my periods were due on 5th of june but they are 4 days late i have taken two pregnancy tests one on monday the other on wednesday yesterday and they show negative this has never happened, could i be pregnant since i had sex on the ovulation day and the egg was already released, and the tests say negative because i have low hcg hormones? please help am desparate