Could Levonelle One Step Cause Early Periods?

hello. I am 18, I took levonelle one step on the 8th of march. I started to have heavy vaginal bleeding on the 14th of march, 3 days ago. I have had this for 2 days and am still bleeding now. My period was not due till the 25th. I have chronic fatigue syndrome and hypothyroidism. I have been on medication, hormone treatment for my hypothyroidism for a year and my bloods are fine. I take hermal remedies to help with my chronic fatigue syndrome, including st. johns wort and magnesium. I wanted to know if this bleeding could just be an early period? If not what should I do?