Bleeding after morning after pill

[Labyrinthia]

I took the morning after pill the 3rd day after having unprotected sex. Four days later I started to bleed - about a week before my period was due. I assumed it was an early period except it's quite light compared to usual. It is now 8 days later and about to stop I think. My periods are usually about a week long.

If this was just a side effect of the pills would it last this long? Or is this my real period? I've heard that light periods after the map could mean pregnancy?