If i had condomless sex is it still possible for me to get an std even when the guy had tested negative for any? would this affect me having oral sex?

Define STD: The common screening tests for a male would include syphilis, gonorrhea & chlamydia, which are curable with meds.Men are rarely screened for HPV, which can cause cervical cancer & is not curable. It might not include herpes or HIV,neither curable, unless the tests were thorough. There are another half dozen infections that can pass sexually but are not listed as STD's. Condoms can reduce some risk