Stop in to a urologist sometime in the next year or so, and ask about the veins. They can do a sperm analysis easily and put your worries to rest. If the veins are causing too much warming in the area and it is killing the sperm, you can have a relatively simple procedure done to take care of it, and your fertility will return. But don't borrow trouble, it's simple enough to do a sperm test. You might be very fertile even with the veins.
Thanks for the reply, that has eased my mind a little. I will make an appointment this week.