Hi!
IF your girlfriend was my patient, I would advise the two of you that you will probably be OK. There are some new studies that suggest that the pre-ejaculate does NOT contain sperm afterall. So, I'm happy she is using something reliable for the future, but you will probably be OK. ALSO don't forget that there is emergency contraception -- Plan B and Next Choice available without a prescription.
Good luck!
Dr B
this was the Monday after the first week