Taken Flucloxacillin and now bleeding on the pill

two weeks ago I got given flucloxacillin for a skin infection by my doctor and got warned at the time that it could reduce the effectiveness of the pill. now a couple of weeks on after finishing them. I’m experiencing quite heavy brown bleeding with cramping too. I have had unprotected sex a few times with my boyfriend in this time. am I at more risk of pregnancy with the bleeding?

thanks, Hannah

Brown bleeding is blood mixed with infection.