I'm worried.

My period this week has been super, super light. No heavy flow at all, I haven't had any pregnancy symptoms and I am going to pick up an over the counter test tomorrow. 
However, I've had a rough couple of weeks with work and it has been stressing me out. Now with my period being alarmingly light, I did have unprotected sex a couple of weeks ago and it was on the last day of my period. 
If anyone can share advice or relate, please tell me. I am freaking out, I don't want to be pregnant, I don't want to have kids in general and I am terrified. 
Thanks.