Confused

My husband and I had sex on May 1,3,5, and 7. I took an ovulation test the morning of the 9th and had peak ovulation so we had sex that morning as well. It's been 3 weeks and my period is late. I took a pregnancy test on Thursday morning and evening... Both negative. Took a test yesterday, Sunday, morning, negative. I'm not stressed from work, as I'm a teacher and schools over for the summer.... So am I testing to early? Stress delaying period? I'm at a loss as to what's up...