BURNING tip of URETHRA immediately after encounter PLEASE HELP

[looking4acure]

About 20 days ago I made the terrible decision of going and getting a massage that resulted in an unprotected hand job. It was my first time in a place like this and I was so on edge the entire time that it didn't last more than a few minutes before I got up wiped all the oil off and left. Within an few hours of leaving I felt a burning in the tip of my urethra that has persisted ever since. It is in a very distinct area the first inch or so of my urethra. My ONLY relief is AZO over the counter. I went to a urologist and got a urine test and CHLA/GON urethral swab done. All came back negative. Since that time I have taken 7 days of DOXY, single dose of AZITHRO, and FLAGYL with no relief. I realize that STD symptoms would not show in such short time after exposure but I do believe that something got into my urethra and has not been affected by these antibiotics. I am going to get a full panel done but I am confident that I will test negative based on my exposure. Since then I have developed a little bit of lower abdomen (below the belly button) pain but I'm not sure if this is because of the medications. I am 24 years old and I am desperate for any help that's out there. Has anyone heard of a similar condition or ANY recommendations for what further testing I need to do. I am extremely scared that I will have to live with this unknown condition for the rest of my life if I don't act quickly. PLEASE respond with any information or related topics.