Given the data you provided, there might be a possibility that you experienced a hormonal imbalance in a period that your organism needs to balance itself after taking the pill and maybe your ovulatory cycles have come back after taking the oral contraception. The body usually needs 3-6 months to regain its own cycles. Moreover, the possibility stands that you might be pregnant and still have your period, but slightly lighter (even though there was no ejaculation inside, there might be a certain number of spermatozoids in pre-ejaculation lubricating liquid). Therefore, it is recommended that you do a home urine pregnancy test, but approximately 3 weeks after the suspected unprotected intercourse which was in the time of your ovulation (mid-cycle time in your 28-day-menstrual cycle). The test shouldn’t be affected during bleeding, if you make sure blood does not mix with the testing urine. Due to the severe symptoms and pain, you might want to see your family doctor or your gynecologist, who will prove or exclude possible suggested conditions.