We understand how worrying this is, when you have done the right thing, and then get let down by the equipment. As far as your STD and STI testing needs are concerned, in this situation both of you should have a full STD screen as infection could go both ways.
This will test for: HIV, Chlamydia, Gonorrhoea, Syphilis, Hepatitis B, Mycoplasma and Ureaplasma. If you think that your risk of HIV is low, you may want to consider the Peace of Mind test which tests for Chlamydia, Gonorrhoea and Syphilis at just 14 days after any incident you are concerned about.
Everyone’s circumstances are different, and it is your responsibility to choose the tests that are right for you depending on your sexual activity and what you know about your partner. If you are unsure then Better2Know recommends a Full STD screen. Once is enough to catch an STD, STI or HIV.