What Causes Long Periods For More Than 8 Days?

Hi, I'm 29 years old and my period has always been very regular. last week I started my period about a week early and I just be finished, but I'm still bleeding a little and I'm on day 8. I am traveling and in a different country and was also on a antibiotic a week and half ago for a Urinary tract infection (it is no longer a problem). I'm wondering why I'm still having my period?