Are you taking these medications? Discuss your ED with your doctor
Anti-depressants and anti-anxiety medications are well known to reduce sex drive and may also cause ED. These include Prozac and Zoloft among others.
Antihistamines such as Tagamet and Zantac can reduce erection quality.
Most high blood pressure medications can play havoc with erections and cause ED. These include Zestril, Tenormin, Clonadine and virtually all others including “water pills” (diuretics.)
Almost all pills for Parkinson’s disease and for chemotherapy can cause erectile dysfunction.
And many medications used to treat prostate inflammation
Source: http://www.nlm.nih.gov/medlineplus/ency/article/004024.htm