Could I be pregnant?

I'm not sure if I am testing too early, or If I am just so stressed that my period is late...but I am 3 days late, NEVER this late. I had sex on Sept. 1st. Ovulated on August 31st.. we had sex 4x that night, if that even matters.. lol. But my question is, am I testing too early? Ive taken 3 tests over the last few days and they are all negative?