I'm not sure about something - do you have adequate erections when by yourself? If so, you don't have a physical problem, it would be more psychological in nature. Almost all guys have a bad outing at some point when with a partner, and that can freak us out & cause us to start worrying if we'll get it up, which just leads to more ED problems. Take it slow at first (especially with a new partner), tell her you just want to have some fun but not intercourse. Then after a few times enjoying that, you'll probably regain confidence & may be able to resume intercourse. Hope that helps...
What are your prolactin levels