Hi, I ve been on Loestrin24 for 6 months now (just finished my 6th pack of active pills yesterday), and have been taking Amoxicillin for 5 days. I had unprotected sex twice last night (he also withdrew before ejaculating). I asked the pharmacist today, and she said that Amoxicillin affects effectiveness of the birth control , but not so much that I need Plan B (because it s only for people who have no type of protection at all). I m still concerned. Should I use a back-up pill (Plan B) today? Also, should I continue my birth control as normal? I should be taking my brown pills starting today, but I m worried about the Amoxicillin and birth control interaction. Plus the sex without condoms , especially because there was another penetration after the first ejaculation .