Dude,

You need to go to a Chiropractor! Trust me on this one. I have had what you are describing all my life on and off. It is from a pulled/strained muscle in back and goes down your keg and into your nuts because of the way the muscles are connected. I had exactly what you have. Chiro does not hurt, it is actually kinda nice having your back cracked. Sometimes the pain will go straight away and sometimes it can take a week or two for the pain to go. Check your sitting and sleeping position and maybe a big pillow or stuffed toy between your knees at night. But it is from muscle in your back or spine that needs re aligning. CHIROPRACTOR!!! Hope this puts your mind at rest.