Hello, Thank you for asking your query at DoctorSpring
Amoxicillin can make birth control pills less effective. You should have notified the dentist that you are on birth control pills. The dentist would have gone for alternative drugs like clindamycin. However, I advise you to use a backup method of birth control like using condoms while taking amoxicillin to prevent an unwanted pregnancy.
As you say you have had sex a week back when you were on amoxicillin, I suggest you go for a urine pregnancy test after a week to be on safer side.
Hope this helps.Please feel free to ask follow-up questions