Thanks for the query.
Emergency pill can alter the menstrual cycle depending on the period of the cycle when the tablet was taken.
As you have taken the tablet in the first half of the cycle, it might have preponed your menstrual flow by leading to withdrawal effect.
The possibility of pregnancy
is less in your case, as you had intercourse in the first week of the menstrual cycle and as you took the emergency pill.
So, possibly the bleeding you had could be due to emergency pill only.
Repeated usage of emergency pills can lead to menstrual irregularities.
So, better to choose some regular method of contraception