There could be various causes for your erectile dysfuntion which ranges from psychological reasons to physical reasons.
The most common psychological causes range from
Guilt about past failed sexual encounters
Having affair with someone else's wife
Having doubts on your wife etc.
Common physical causes apart from high blood pressure
Leading sedentary life
,taking alcohol,taking medications for high cholesterol
or anti depressants etc.
What to do...
Do regular exercises
Reduce your weight and try to be in your required BMI
Quit alcohol and smoking.
Do yoga and deep breathing exercises
You should improve with these suggestions but if you don't improve then,it would be a good idea to consult a urologist
and get managed properly.
There are medicines like VIAGRA ,which can be used,but after talking to your doctor.