It feels like a pulled tendon, or muscle only on one side, behind the scrotum on the left side. I feel it sticking, or raise up, tightened up. It hurts when I lean forward sitting and when I'm in the car sitting and experiencing a bumpy ride. Also when I bend over to get something off the floor. What could it be. It hurts and almost goes away but it is back.

You'll need to see your doctor. There's no way for anyone to diagnose over the internet.