Period started early?

I'm not supposed to start my period for another 8 days. I wasn't able to pay for my birth control this month, so I've gone about a month without birth control and I would be on the last week of hormone pills today.

I've also been exercising pretty heavily (I don't exercise often, so anything is extra to me). Is it possible that the exercising kick-started my period?

I also have PCOS. Is this dangerous? Is it bad to start over a week earlier than I'm supposed to?