If what you think is your period came on the exact day it was supposed to you cramped really bad the 1st day and bleeding was heavy for 2 days and then light for 3 is pregnancy possible or paranoia?

Pregnancy is always possible, I suppose, but my educated guess is that you are just nervous (the actual term "paranoid" doesn't mean nervous, it means the fear that people are out to get you). You had what sounds like a completely normal period.

If you are truly concerned, please contact your doctor.