Stress?? Pregnant?? Anybody??

I apologize ahead of time if this is tmi. However, I've never experienced this before and I'm a little confused. So, I started my period 4 or 5 days early, VERY strange for me. Then, it only lasted for 3 days. The heaviest day, I only had to change a tampon once. Since then, I've been continuously nauseas, sensitive to smells, and moody. Has anyone experienced this before? What was the cause? Thank you :)