Late.

So of course... my period is late. I had sex on my ovulation day, but we did use protection the entire time. The condom wasn’t expired or anything. So anyways I’m 2 days late. Lately I’ve been having early periods, or late. Over the weekend, I was stressed about things with my theatre audition.. so I’m not sure if that could be the cause of my late period. I did take a test and it came back negative. Not really worried much about being pregnant... but it’s still in the back of my mind. Any advice?