Edit: I posted this, below, before I realized that the rules here are that the Health Nurse answers questions. However, I have had the same problem that the original poster mentioned, and over the years found very little information about this
specific issue in PubMed abstracts or from doctors. Years of therapy did nothing to help, but Viagra did. Viagra and anxiety-based ED is a pretty narrow topic and I don't think there's much hardcore science on it. So I hope my personal experience will be helpful to the poster, but I defer to the Health Nurse when she/he can respond.
"Is viagra any help in this situation?"
Yes. Absolutely.
At least in my lengthy experience. I assume that you're physically healthy and everything works normally when you're practicing alone.
Turtling is probably from the flight/fight response to stress. Fortunately, Viag and the other PDE-5 inhibitors restore the normal nitrous oxide chemistry of erections.
You won't get an erection until you have a sexual stimulus (visual, tactile, dirty talk, or your wickedly dirty imagination). Given a sexy receptive partner you're good to go. It won't make the nerves go away, but you won't need to worry about whether the python of love can stand at attention.
The only thing to consider is the dosage. For me 25mg of V is good enough when I'm relaxed but feeling just a little worried. 50 mg is more reliable in the sense that I don't lose rigidity if my mind wanders or playtime gets interrupted. 100 mg can be too much. Big meals slow down the absorption, so timing can play a role. Cialis lasts much longer and solves the timing problem if you take it hours before playtime.
My suggestion: experiment with smaller doses first and see what works for you.