Hi! My Period Started On 11th May.i Had Sex With

Hi! My period started on 11th may.i had sex with my boyfriend on 18th may night. Took the Ipill on 19th afternoon( which is less than 24 hours) . Started bleeding on the 31st may that is 12 days after the pill. Had very light bleeding for 3 days. Was expecting my period on 6th June. I have a 25 day cycle usually or sometimes 30days. Can I be pregnant? Is that bleeding caused by the pill, an early period or implantation bleeding?