Can Trimethoprim Lower The Efficacy Of Birth Control Leading To Delayed Period?

Hello. I last had a period on the 17th march, 2 weeks a took a 5 day course of Trimethoprim, since then I have had unprotected sex. I am on Cerazette and carried on taking it throughout the course. Would they have effected the pill, delayed my period or is there a chance that I'm pregnant?