What Causes Missed Periods After Taking Contraceptive Pill?

i;ve been married for one and a half years. six months ago i had an abortion. after that i was having my normal menses. i had sexual intercourse with my husband on 4th sep and took a contraceptive pill after a day. then on 7th sep i had my periods. after that we didn't had sex. it's been almost two months that m not having menses.is there any slight chance that i could be pregnant????