Not necessarily. Maraming reasons bakit nadedelay ang period ng isang babae aside from pregnancy, like stress, diet, sleeping routine, etc. Or simply because "trip" ng body...
Again, depende po. Nung "kabataan" ko when I was not sexually active at all, I can get as much as 2-3 weeks delay due to stress alone. Then maybe upto 1 week on a normal basis, even now. Although in general ay regular period talaga ako but I'd get some delays every once in a while.
Tere SC