Missed period...

I'm kinda freaking out:/ its been almost two days of when my period was supposed to start. I have traveled and my body has been going through environmental changes. But at same time I did have unprotected sex. But we used the pull out method lol anyways i toke pregnancy test today and it was negativeTHANK GOD!!! Is there chance I can be still? Or missed period is because of stress/ travel....