I had unprotected sex 3 days after stopping my antibiotics while on the pill, i then carried on the pill and have belly aches for about a week now?

Infection?: If you had unprotected sex and are now having pelvic/abdominal pain, it is possible you have contracted a sexually transmitted infection. If you are a woman, it is also possible you are pregnant. You might consider making a dr. Appointment to get checked out; you can also discuss contraceptive options with your dr. There is also a chance that your pain is unrelated to sexual activity.

Home Pregnancy test: Different antibiotics can remain in your blood stream for varying lengths of time. So, yes, there is a chance that the antibiotic you were on might have decreased the effectiveness of your oral contraceptive pill. Regardless, there is always a slight chance of getting pregnant on the pill so take a home pregnancy test. If the test is positive, make an appointment with your doctor.