Short period

I'm a very regular gal, my period is 4 days long. Never shorter, never longer. But this time it was only two and a half days long. The thing is, my husband and I went full on all the way a couple of days before and up to a week before my period, I tested right before I started but of course I got a negative result. Am I just being paranoid or has anyone else had this experience and been pregnant? Thanks!