Thanks for your question. You don’t need to freak out about getting HIV this way. HIV is not passed through oral sex, even if someone cums in your mouth.
You could be exposed to other infections through unprotected oral sex, though. (Check out the charts on “my chances” to see what kinds of infections get passed through different kinds of sex.) Even if someone doesn’t come in your mouth, it’s possible to get Gonorrhea, Chlamydia, or Syphilis this way. We’re seeing very high rates of Syphilis among gay and bisexual men in Vancouver right now, so it’s a really good idea for men to get tested regularly.
Let me know if this is helpful,