For the past couple of months I've noticed that when my scrotum is relaxed, it feels like there is a vain on the side more towards the front of my left testis going up and down. I think it is the Vas Diferens moved to the side, instead of staying in the back, but im not sure. It isn't always like this. Only once in a while. When I notice it I could rotate it back to the back. Is it normal for my testical to move arownd like this or is somthing wrong? Its only on my left side.

Has anybody else notice somthing like this?
Thanks,