The Sexual Health Inventory for Men (SHIM)1 is the standard questionnaire used by doctors to categorize Erectile Dysfunction.
Note that the SHIM questionnaire will not diagnose the cause of your ED. Diagnosis will require a medical examination by your doctor.
If you find that you have Erectile Dysfunction, you should see your doctor. There are many different causes for ED, and it may be a symptom of a serious medical condition. Your doctor can determine the cause, and recommend appropriate treatments.