Welcome to the forum. Thanks for your question.
Oral sex can usually be considered safe sex. There is a low risk for all STDs and virtually zero risk for some of them. This has been discussed previously; please read the questions and replies in the threads linked below.
In theory, the possibility of HIV transmission might be elevated if blood were present, but the transmission risk is so low that a slightly higher risk makes no important difference.
The hepatitis B virus (HBV) is one of the STDs rarely transmitted by oral sex. Anyway, if you indeed were vaccinated, you can consider yourself immune. It should be possible to dig out your immunization records -- e.g. by contacting your childhood pediatrician's office. If not, a blood test can tell whether you have had the vaccine and/or have had a past HBV infection.
Syphilis is common in gay men and once in a while is transmitted by oral sex, but is very rare in heterosexual women and oral sex with female partners would carry almost no risk. There are risks for gonorrhea and nongonococcal urethritis (NGU), and little or no risk for chlamydia.
Best wishes-- HHH, MD