Receiving unprotected oral sex is lower risk than unprotected vaginal or anal sex.
You can get gonorrhea, chlamydia, syphilis and genital herpes type 1 (if you don't already have oral herpes type 1.
Syphilis is uncommon in most developed countries. I wouldn't worry much about that. You can test for that at 6 weeks if you feel the need to.
You can test for hsv1 if you want, but the hsv1 IgG blood test is unreliable and misses 30% of infections. If you don't get sores by day 12, I wouldn't worry about it. If you do decide to test, it can take up to 12 weeks to develop antibodies. If you test positive, it won't tell you where you have hsv1 - orally (cold sores) or genitally. You can have oral hsv1 without ever getting symptoms.
If your tests for gonorrhea and chlamydia come back negative, and you want to test again, don't take any more meds, and test again in a couple of weeks.
I wouldn't overly worry. Most experts feel that one encounter of oral sex doesn't warrant testing.