Quoting Lana Del Rey:" Just curious, have any of you ladies had 17 days in between the last day of your period and the first ... [snip!] ... a week after my period ends. Which I guess would make sense if my cycle is so short. This happened my last cycle too. "
For one, you should count your days from the start of one period, tot he start of the next. That's generally how they go.
I've had a few really short ones (17 from the start of one until the start of the next). If it's just once, then it's just an odd period maybe because of stress. If it's ongoing, then you'll want to get checked out. I think that 25-35 days is considered "normal." but sometimes people use slightly different numbers.