Thank you for your query at DoctorSpring.com
This is Dr Goel again.
Talking of immnostimulation, there is drug available by name of OM 89. However in limited trials it has shown effect as good as placebo only.
You can consider shockwave therapy to prostate. It has shown good short term results in few series. However, I don't have used it personally.
I usually put my difficult patients on tadalafil 5 mg along with alpha blocker and it certainly makes them feel much better. This is not FDA approved use of tadalafil; it is usually used for treatment of erectile dysfunction.
Take your call and try any of the three or all three and you never know what works for you.
Feel free to discuss further,