I've been on amoxicillin for treating a skin condition for about two months. I started taking tri sprintec birth control a month ago. I stopped taking Amoxicillin 4 days (I think) before my period started and I took the week 4 sugar pill BC. I had unprotected sex today, Sunday of the next 28 day tray. Since I was worried in the after thought of getting pregnant I took a second dose from week 3. Am I protected? Should I take plan b?