I am not an expert, but I can suggest several things you may want to talk to your doctor about. 1)Hormone Levels- they may check for free testostorone and total testesterone. They may check for other hormonal imbalances. 2)Depression/Anxiety- this is what created both a decrease in libido in my situation. The SSRI drugs actually helped me reduce some of these symptoms, but I am still not ruling out any hormonal issues. 3)Venous leakage- if you had any major injury or trauma in that region you may try exams to see if any arteries are blocked or impaired in the penis. 4) Medications- you may be on medicine that can be causing these side effects.
These are just suggestions, but questions you may raise with your health care professional.
Yeah go to an endo or good urlogist I would think this problem is either caused by excess estidol, low t, or dht levels
Think about it like this a man in his 80s will not be as large as when he is 18