I Had Light Spotting On March 17 That Lasted For A Day. My Normal Cycle Started On The 20th Of March But It Only Lasted 3 Days When It Normally Last 5. Then On April 2nd My Cycle Came Down Again. Could I Be Pregnant?

I seriously doubt it. If you have had a period, you most likely are not pregnant.

The length can be different depending on many factors, a few of which are hormonal levels, age, stress, etc.