What Could Be Causing Loss Of Erection And Anxiety Or Shivering Just Before Intercourse, Even After Viagra?

Hey Before an intercourse I get a normal erection but just when I try to enter my penis in the vegina I lose the erection and my excitement turns into like a anxiety and if the weather is little bit cold I start shivering. I do regular exercise and I don t smoke nor drink but still face this ed issue, last time I faced the same issue even after taking a Viagra