Welcome to our Forum.  Few STIs are acquired from receipt of fellatio. There are no descriptions of HIV being acquired as a result of receiving fellatio.   Gonorrhea and NGU are the most common and typically have a penile discharge as part of the presentation.  Isolated testicular discomfort is almost never a symptom of STI. 

In your case, your negative tests are further strong evidence that you were not infected in the course of the exposure that you describe.  Even though the ceftriaxone/azithromycin would have begun acting on any infection, residual, dead material from treated organisms would still most likely be present.  Further, I think the hydrocele you have now detected may also be related to  your discomfort.  My advice would be to not worry further about this encounter- no further testing or treatment is needed. 

I hope this comment is helpful to you. EWH

---

Ok thank you. I just got a little worried because I read that hydrocele could be the result of epidimitis which comes comes gonorrhea chlamydia. I know hydrocele also could be the result of something else other than an sti. Thank you again

No reason to worry.  Hydrocele's occur naturally and are not a typical consequence of epididymitis.  You have no medical reason to fear that you have an STI.  EWH
---