I was taking Amoxicillin 875 mg twice a day for ten days for a strep infection. I have been taking Microgestin Fe 1/20 for a year. No where on the Amoxicillin bottle did it warn about messing with birth control. I had unprotected sex with my boyfriend within the first couple of days of taking Amoxicillin. Now my period is late and I am concerned that I may be pregnant. What are my chances?