How can I know if I have gotten an STI?

[revellance]

I had a terrible lapse in judgement and slept with a prostitute on March 9th, the occurrence happened at about 2:00 am.  I received about a minute of unprotected oral sex and then there was protected vaginal penetration for about 10 minutes.  By the middle of the day on March 10th, I was feeling a slight urge to urinate in my urethra (not my bladder).  This sense of urgency increased a bit over the course of the next couple of days, but it was not as bad if I drank a lot of water and took so cranberry supplements from the store.  Also the evening of March 10th, I appeared to be developing a slight rash at the base of the shaft really in the pubic area that was irritated, but did not burn or hurt unless I rubbed it with my clothing.

March 12th, I went to the doctor and explained all the symptoms I was having and the doctor wrote of the rash as folliculitis given that the pimples appeared to all be around a hair follicle.  They assumed that it was bacterial and attributed my urinary issues to this same problem.  I was prescribed a topical antibiotic ointment that I applied (3) times a day for (7) days.  The redness and the pimples went away, but you can still see where they were (almost as if they are still healing, just the skin is no longer irritated).  I was also prescribed a seven day course of Bactrim to treat the urinary symptoms I was having.  I completed that course of antibiotics to no avail and am still experiencing urinary symptoms.

The first doctor I saw sent my urine culture to a lab to test for chlamydia and gonorrhea, which both came back negative.  They did not mention whether or not they looked for any specific bacteria that could be causing UTI symptoms.  

March 21st, I went to another doctor for a second opinion.  I told him the entire back story and about the other doctor I had seen and what they had resolved the issues to be.  He looked at the area where I had experienced the rash and he was extremely confident that this skin issue was not related to HSV-1 or HSV-2.  As for the urinary symptoms, he said that he would examine the urine again, but upon initial examination of my urine he saw nothing that suggested an STI.  At this point he has resolved that the urethra may be irritated, either from soap, detergent, brushing my clothing etc.  

I explained to him that my feeling of needing to urinate was not in my bladder, but rather in the tip of my penis and that the urethra opening and the entire tip of my penis felt irritated.  Not painful necessarily, but just a bit irritated to the point that I am having a feeling toward the end and opening of the urethra that is making me feel like I need to urinate.  He put me on a (3) day course of Phenazopyridine that I am on my second day of taking and the feeling is a bit less noticeable, but is still there.  He also recommended that I apply an OTC A&D Ointment to the tip of the penis, the opening of the urethra, as well as a bit just inside the urethra if possible.  

I started applying that ointment last night and again this morning.  They also sent my urine culture off to look for signs of an STI (at my request), but he was certain that I would not have seen a false negative on the culture that was previously sent off to the lab.  

At this point, I have no idea what is causing this issue and I am incredibly worried I have an STI causing this that cannot be detected in a urine culture, despite the popular belief between these two doctors that it is unrelated to the sexual encounter that I had recently.  

I am incredibly worried at this point and am waiting for the results of the urine culture to come back in a couple of days, but I need peace of mind I guess.  

Does anyone have any advice, additional resources or information that would help me through this?  Could this be some STI other that Chlamydia or Gonorrhea based on the information that I have provided above?

Help please!  

[revellance]

So I got the results from the urine culture back and they were again negative for chlamydia and gonorrhea.  So at this point, I'm not sure what is going on.  The Phenazopyridine is starting to help with the urinary symptoms that I was experiencing, but the feeling is still there.  Just faint.