After receiving unprotected oral sex, how likely am I to contract?
No, dude, take precautions before you have sexlike having STI tests done before you get intimate, using condoms or dental dams, eschewing one night stands, etc. Youre not terribly likely to get any of these things from oral sex. Just how skanky was your partner? If you think you were exposed to an STI, go see a physician for testing and then follow his treatment plan, if any. Taking antibiotics indiscriminately is a good way to develop immunity to them. Self-medicating with any medication that has not been prescribed to you is foolish.