Thanks for Query.
I think your family Physician has given a right advise that your ED was due to Diabetes
diabetes causes Libido & ED is a common feature in it.You had taken Penegra
50 & get Erection its fine.i think you should go for it.
had advised for penile Doppler test to confirm blood flow to penile artery I think that is not required at this stage as first possibility is diabetes induced ED.
also causes other symptoms not only loss of libido.so that test is also not required.Thanks again