First you need to know that chronic prostatitis is not addressed well by the medical community and so if you really want to treat it properly, it will take some work, including a change in diet, some supplements, and development of some good habits.
I too have been suffering with it for over a year but it has thankfully been getting better as I have been following a protocol of diet change and supplements. I also tried 3 different antibiotics over the last 12 months and I too only got limited results, plus the side effects from the antibiotics were horrible to say the least.
First I began following a certain doctor's protocol (not sure I am allowed to mention who) for prostate problems, with his herbal tincture saw palmetto/corn silk/pygeum/zinc formula plus following a vegan, mostly organic diet. Often the pesticides and steroids in the non-organic meats, dairy, and produce are what lead to an enlarged or diseased prostate because they mess with your hormone levels. Also, the pesticides and other chemicals get lodged in your prostate, which is a small gland, creating all sorts of havoc and disease.
I also made other changes in my diet yet again to try to help my prostate, based on all the stuff I've researched. Highlights include to especially avoid caffeine, alcohol (yes, ditch the beer), soda (any kind), chocolate, white sugar and white flour, orange juice, and any spicy food. You must also check to see if you have any food allergies (mine was gluten - i.e. wheat, oats, rye, and barley) - that can cause problems as well.
I also started taking zinc and quercitin w/ vitamin C. Quercitin apparently helps to lower inflamation. Another important supplement for the prostate is selenium.
Sitting in hot baths for 15-20 minutes at a time will also help lower inflammation in the prostate. I did that for a few weeks. Prostate massage is also helpful if you can get it or figure out how to do it yourself (that is not easy).
In 2 months of this I noticed a great improvement in my prostate - the last doctor check revealed that my prostate had gotten softer and smaller from when I started. Alot of the pain is also gone now, especially in my right testicle. I would say most of the pain though was from the pus which was in there and has since come out on it's own, hopefully as a result of the methods I have been following.
Also, I also have to tell you that if you are or have taken antibiotics for any length of time, you really need to take a probiotic to replace the good colon bacteria that any antibiotic kills off. Without replenishing this bacteria properly, you end up with more health problems soon down the road, such as Candida/yeast problems, constipation, fatigue, foggy brain, and many other potential symptoms. had to find this out the very hard way over the years.
Candida/yeast can also cause urinary tract infections and prostate infections, so at this point you may wish to see if you have that as well.
At this point you may wish to check with a naturopathic physician to help you get onto a good protocol for treating this is all the above seems too overwhelming to start/follow on your own. Don't worry, there is hope for healing from this beyond traditional medicine, in fact often traditional medicine fails in treating prostate problems effectively. Antibiotics do not always get into the prostate in enough quantity because the glad is small and the blood vessels are very small. But if you address the overall condition that affects prostate health, you can often find relief and better health to boot.