The day of unprotected sexual contact the first time was followed by administration of the emergency contraceptive pill
which resuces th3 chances of pregnancy
But then you had unprotected sexual intercourse again, this second time is the worrying date of contact. If you were to get your period it should have been on the 4th. You did not experience this.
Pregnancy is the first thing that will have to be ruled out but this will have to be conducted at least 2 weeks after the suapected date of conception or on the first or second day of a missed period.
Contraceptives can also be a cause for menstrual irregularities; but this and othercauses can be assumed once pregnancy is completely ruled out.
Hope this helps.