If so what is the treatment?  

The exposure you describe was low risk for STIs, even if the person performing fellatio on you had just performed fellatio on someone just before you.  I presume that it is unlikely that your friend had gonorrhea or any other STI and it is statistically unlikely that your partner did either.  Further, a scratching sensation is not a typical sensation of STIs and your symptoms began occurred sooner than is typical for sensations due to STIs (typically urethritis symptoms begin about 3 days after an exposure).  Further, urinary frequency is not a sign of urethritis but may reflect anxiety or a UTI.  Finally, your tests for STIs are negative, ruling out any typical STI.  You can confidently rule out typical STIs.

I'm curious as to why you had your semen tested rather than urine.  A more typically test for symptoms such as yours would be a urinalysis looking for white blood cells and a urine culture evaluating for a urinary tract infection (UTI).  

A further comment- E. coli bacteria are normally present in the urinary tract even without infection and thus I am not surprised to hear of the positive culture.  It would be unusual for E. coli to be introduced into your urethra from oral sex- these bacteria are uncommon in the throat.   If there were substantial numbers of white blood cells present on a urinalysis that could be due to either a non-STI UTI or, more likely, the syndrome referred to as non-chlamydial non-gonococcal urethritis which is thought to occur when new but otherwise normal bacteria are introduced into the urinary tract.  This can certainly occur following receipt of oral sex; when it does it is typically self limited and is not a threat to sexual partners during unprotected sexual intercourse.

How long ago was this exposure?  Are your symptoms still present?  Are they improving or getting worse?  EWH

  Symptoms came on directly two days after oral.  Very obvious urine issues. And urine smelled foul.  Nothing ever found.  I read stories like this on the net over and over and over.  Guys get uti symptoms after oral and no bug is ever found. And they develop prostatitis.   Is there any explanation for this?  Thx 

The people who develop UTI symptoms, following receipt of oral sex, most likely have non-chlamydial non-gonococcal urethritis, which is a self limited process, and, unlike your situation, is manifest by the presence of white blood cells in a urinalysis. Your situation is different.