Ellaone and period

Ok so I was away with my bf and on one of the nights when we were having sex, the condom split when he finished. I'm not on bc at the moment. So we made sure to go and get EC in the morning, boots gave me Ellaone.

Basically at that point my period was due in 4 days. It arrived the day after taking the pill. I'm just wondering if this is definitely my period, just a few days early. Or if its some other bleeding that I should be worried about?