Oral sex is considered a low risk. Saliva does not have enough HIV to cause infection. There are other Sexually Transmitted Diseases (STDs) that one can get though. The person getting oral sex just lies there

but the person giving oral sex is more at risk as they are coming into contact with sex fluids. As Homerx says, it depends on your oral hygiene at the time.
For example, if you had just eaten sharp chips or just brushed and flossed your teeth, you should wait at least an hour to perform oral sex as those things are a way into the bloodstream. Remember the virus is so tiny and needs a tiny cut, sore, puncture, or tear to get into the bloodstream.
If you performed oral sex and swallowed the cum and you have a sore throat, you may become infected with anything the man has.
Always use protection as Homerx has said. They have flavored condoms for this sort of a thing.
If you are too worried, get a test three months after the supposed point of infection.
All the best
Muthoni (Mson).