So I am on birth control, but I got a sinus infection and I have been on amoxicillin for a week. I took the last antibiotic yesterday. Last night my boyfriend and I were having sex while I am on my period, and the condom broke, neither of us noticed. He pulled out because he always does, but I want to take a plan b. Will the antibiotic affect it especially if I took the last one yesterday and I take the plan b today?