So frustrated another negative and no af

I'm so frustrated. I'm going on 4 days late and I just took a test but it was negative. I'm never late even when I'm stressed. Is it because I took it in the middle of the day? Anybody else have this issue? I had unprotected sex on the 15 which was my ovulation day. Am I doing something wrong? I'm queasy, throwing up have headache backache and super bloated. More bloated than I ever get with af.