I really need help.

Marissa • I`m twenty-three years old. I’m also a mommy! I love every bit of it.
I am seven days late for my period. When I was three days late I took a First Response pregnancy test and it was negative. I plan on taking ClearBlue tomorrow. But I really don't want to be pregnant. It's not time for that yet. I feel like maybe it's just stress because I have been a little stressed lately. With me being so worried about this, it just adds on to the stress. 
Have any of you been a week or more than a week late and then got your period finally after being that late?
I really need opinions. I'm so worried..