The only time I have issues like that is due to certain pairs of underwear. The combination of sitting and something odd about that certain pair can cause a throbbing pain for me.

But, the back pain could very well be related. I wonder if you don't have a kidney infection. That system is connected and I wonder if the pain from your back might be triggering the pain your testicle. You might try cranberry juice for a while and see if that helps?