It really depends on what type of sex you and your partner are comfortable with.
There is a much lower chance of passing HIV from unprotected oral sex when compared to unprotected vaginal or anal sex.
Have a look at our “Know your chances” web page, it provides information on your chances of getting or passing an STI depending on how you are having sex.
Having an undetectable HIV viral load would also reduce the chance of HIV passing.
Not having a sexually transmitted infection (STI) will also reduce the chance of HIV passing. I don’t know your personal situation or sexual history but it is common that many STI do not show symptoms, given this we recommend that people go for STI testing. How often you get STI testing really depends on your personal situation. Have a look at our page on when to test.
To reduce the chance, it is also good for the person performing the oral sex to have a mouth in good health e.g. no sore throats, no infected teeth, no STI in mouth etc…
The chance of HIV passing to your girlfriend with you having an undetectable viral load and both of you being in good health would be very low.
Even if the chance of passing something is very low it really depends on how people feel about the situation. It can be difficult to enjoy sex if someone is worried about passing or getting HIV.
Not cumming (ejaculating) in your girlfriends mouth or using a condom for oral sex are two things to reduce the chance of HIV passing.
Please leave a comment to let us know if this answers your question or if you need more information.
For other readers, please feel free to leave a comment, or let us know if this was helpful.