Welcome to Healthcare Magic
You probably are suffering from erectile dysfunction
. It can be because of excess stress
. Try to relax and don't have anxiety
. You will be able to satisfy your wife well. Engage in foreplay with wife as this makes erection easier also before immediately having sex. You can ask your wife to masturbate for you as this is a good technique to improve strength when you feel less strength. If there is still problem, better to go to Urologist
and get tested for Diabetes
and other causes, do urine examination also. Good treatment is there for this like medicines, pumps, surgical also.