There is a whole other thread at this site with people that have the same exact problem. The similarities are striking.
I've had all those tests you've mentioned and have ruled out everything except Interstitial Cystitis.
Over 80% of males that are diagnosed with non-bacterial chronic prostatitis are misdiagnosed and instead have Interstitial Cystitis.
This is currently an incurable disease, but A LOT MORE medical research has been done on it in the last 2-3 years.
The problem is that most doctors (including urologists) are clueless when it comes to Interstitial Cystitis.
As a patient, you will feel like you are spending a lot of money, constantly going to doctors, and getting no help.
I can tell you that at least 90% of the people on this other thread have exactly my symptoms, and are only symptoms of Interstitial Cystitis.
Doctor, if you are not one of the men who have experienced this life ruining experience, count yourself lucky.
http://www.medhelp.org/posts/Undiagnosed-Symptoms/Periodic-tip-of-penis-pain-after-ejaculation--burning/show/201292