Just confused.

I started spotting the day before my period was supposed to start, the day it was supposed to start the spotting picked up. (It wasn't enough to wear a pad or Tampon) The color was a light pink-brown ish. This only happened for 3 days altogether and just stopped. My period lasts 4 days, and it's normal on the heavier side. I was so sure I was pregnant and yet haven't tested positive. Any advice or similar stories that ended in a pregnancy would be helpful.