Natural remedy to ED problem due to head injury injury

Patient: Hello!I am a 40 year old man having problems getting erection. Giving you a bit history of my problem. I had a head injury (gunshot wound) in the head back in 1994 due to which my left side was paralyzed and it severely damaged my nervous system. I used a drug called Tagratol for few years. Over the time, I recovered from paralyzation. Got married in 2001 and used drugs like Viagra to attain eructation for sexual intercourse. I was also blessed with a child.Since the drug is banned in the Country, I live in, it is no more available. Please suggest, what should I do for my problem. Is there an exercise or natural remedy to my erection problem? Who may I consult for this?Since, I used medication to attain erection, I somehow feel dependent on the drug, it may be Psychological.Please help.