I have a question if anyone know the answer

Lola
So I was in a relationship, some stuff went down hill long story short no longer together.
But my question is I haven't had my period in like 2 months (plus). 
And I was wondering is it because of stress?
I've taken pregnancy test so I don't want this to sound like a complete silly question.
We kind of stopped having sex towards the end of the relationship, and we were always supper careful.