As long as you are working with your doctor, and he has prescribed PDE5, I see no problem with that, using it as directed and not overdosing and so on. Perhaps once you get over this anxious period and you are more at ease around your girlfriend, you no longer would need the PDE5. She should understand that men are not always "ready to go" and that there will be times when any man cannot "get it up".
It had also happened with another girl but before this 2 girls was a lady that i did successful without loosing it. Am now so afraid of loosing my girl hence, i've decided to arm myself with a PDE5 after discussing with my doctor, to be taken secretly like 30min before sex because,i wouldn't like to experience that ugly scenario again - what's your view concerning using PDE5 secretly because, i do not like to loose her. Cheers.
It seems rather harsh that she'd quit you because of this, if you explain that it's something new for you. However, I realize that the both of you would be spooked after the third time. Would you consider oral sex, either one at a time or in "69" position? I wonder if that would work until this temporary situation improves? Of course, if it doesn't improve, maybe this gal isn't right for you. Your body may be telling you something that your brain doesn't want to acknowledge. If this would happen with another gal, then seeing your physician would be beneficial.