My period started 10 days before it is due - should i be worried?

I'm 17, and i have a 30-day cycle. Recently i was ill and i had cough mixtures, gastric pills and panadol. My period started 10 days before it is due, and the blood is extremely dark, almost black. I know that medication can cause periods to become irregular, but isn't 10 days early too big a change? My period has never been irregular because of medication, and i am feeling a little worried about it, with the strange blood color and all. Please give me your advice! Thank you!