Does Taking Antibiotics Reduce The Effect Of Logynon?

I started logynon on first day of my last cycle and used backup methods for 14 days as advised, but then on the 14th day, i had to start a course of alphrim (trimethoprim) for a UTI... I took my pill perfectly and took the antibiotics at night for 7 days and finished the course on wednesday. 2 days passed after I had finished the antibiotics, by this time I was on the last active pill in the packet before the sugar pill week and I had unprotected sex on the friday. Does the antibiotic reduce the pills effectiveness? Could I be pregnant?