I don't know much about IC in men, other than it's possible. The test the preform for women is called a cystoscopy, where they insert a tube into your bladder, fill it with sterile or medicated fluid, and take some pictures. The doctors can tell from the pictures if you have IC or not since it's pretty distinctive to look at. I'm assuming the procedure is the same for men. And don't worry, you'll be sedated when this occurs and won't feel it.
I do know that for IC, things like cranberry juice is not good for IC and will make it worse. Also, there is a LONG list of other foods, etc, that causes problems for IC patients, including antibiotics, which may be why you have not seen improvement. If the bottle of something says "Don't take this if..." and you fall into that category, don't take it without a doctors advice.
I don't know much about burning in testicles or penis since I don't have those parts, but have you been checked for things like testicular cancer or any STD's? Have they checked you for prostate issues? Bottom line, if your doctor isn't coming up with anything new or helpful, find a new doctor. Also, checkout www.ic-network.com. They have a whole section dedicated to men with IC.
If the doctor says you have an infection, then you don't have IC. IC is pain and burning without infection. Also, eat tums to alkalize your urine, and see if it helps you pain in the future.