Welcome to HCM,
You are suffering from ED ( Erectile dysfunction
) as you rightly pointed out you do not have diabetes
which is one of the leading cause of organic ED.
In short other possible common causes are.
a) Neurological and Cardio logical disorders like Multiple sclerosis
and impaired blood flow.
b)Any kind of addiction like alcohol or smoking
c) Many medicines if you are taking any.
d)Lower Abdomen surgeries.
is very common cause.
f) Hormone imbalances.
You should approach good qualified Sexologist/ Uro surgeon to examine you and investigate you for your problem with penile doppler studies,detail psychological assessment,hormone studies, and sleep monitoring during REM cycle.
Once any cause is detected it can be corrected accordingly and you should be able to enjoy life.
Now with the development of very good drugs ED is treatable in most cases.