If it's affecting masturbation then Depression also becomes a possibility.
If you hadn't already talk to your GP and a urologist I'd suggest you talk to your GP and if he thinks it's necessary, a urologist. You've had two board certified doctors examine you for symptoms that form a clear pattern of dysfunction and they've found none of the causes that they'd expect to see in a medical ED case. If you're not confident in their prognosis get a second opinion, but before you do, it seems like it would be a good idea to get a first opinion from a doctor that evaluates the other side of the ED equation.