Spotting early.

So, it was a busy morning at work today, so  I finally got to go to the bathroom at lunch - all to find spotting.  And early!  4 days early than my due date.  What is this?  Of course early spotting I am hoping pregnancy, but the negative pregnancy test upon arriving home reassured me that wasn't the case.  No cramps yet, but it's only day one.  I pray that the cramps are light this month.  We don't want any more trips to the ER.