I need some answers

Soo two weeks ago was my ovulation days and I had sex through all of it and yesterday I was suppose to start my period but I didn't and when I don't start the first day I usually start that night while I'm asleep or the next morning but I haven't started. I took a test yesterday but it was negative. How long should I wait to test again? Could it be possible that I'm preganet? Or just late starting?