Weirdly, I have the opposite issue. Hard as a rock for prossies, but often have trouble getting hard for civvies. I think it's because there is more pressure involved with civvies, they have greater expectations and will not be so kind if you cannot perform. Whereas a prossie has seen it all, and it's her job to relax you, get you hard etc.
My only advice would be, as others have said, viagra or cialis. It sounds like there is a psychological reason for it, rather than physical though, so maybe you need to get to the root of that. If you have a wife AND shag random civvies, it's interesting that you feel the need to see WGs on top of all this. Maybe the guilt of spending money on them is fucking with your head, I don't know