It's not herpes, you can rule that out.
I'm not sure this is all from 10 seconds of oral sex. The chances of you getting anything from that are really super low. I'm wondering if the timing isn't just really an ugly coincidence.
Have they checked your prostate? Tested your urine for other bacteria or looked for white blood cells?
I'm assuming you mean cefixime, and it's not the best choice for gonorrhea, no, but it might cure gonorrhea if you had it, but your test came back negative. What was the timing of those tests? Did you wait at least 3-5 days after the encounter to test?
One other possibility is that if your regular partner has given you oral sex, and has been sick, you can get that bacteria (or virus) in your urethra. You can get strep, adenovirus (usually causes bronchitis and other upper respiratory infections), etc., from oral sex. That's why testing your urine for everything is important.
You may need a urologist.
Let us know how you're doing.