Thanks for your query.Based on the facts that you have posted it appears that you have
problem of getting hard erection and penetrating vagina during sexual intercourse due to narrow vaginal opening of your wife.
Your problem of Erectile dysfunction
seems to be mind related and due to performance anxiety
Following measure will help you to boost up your confidence and getting good erection.
1) Practice regular exercise for 45 minutes followed by meditation
for 1/2 an hour in the morning.
2) Take high protein diet rich in vegetables and fruits and Vitamin A
3)Take anti oxidants like Almonds 5-6 everyday..
4) Avoid alcohol and smoking..
Please consult qualified Gynaecologist and get your wife examined to ule out vaginismus
. If needed she can dilate her vagina by perforating hymen manually .