Taking amoxicillin and birth control…what are my chances of getting pregnant?

Patient: I started taking amoxicillin last Monday for strep throat, and I am on Tri-Sprintec birth control pills. The start of my last period was last Saturday. My boyfriend and I have had unprotected sex about 3 times after my period ended; he never came inside, but I know you can still get pregnanat. I’m really worried, and would like to know my chances of getting pregnant.