What could be the likely cause for my sexual dysfunction?

I am a healthy 36 year-old male and I am experiencing prolonged sexual dysfunction. I eat well, I exercise regularly and I neither smoke nor do I drink more than 2-3 in a social situation a couple times a month. I have no major illnesses (diabetes, heart disease) or injuries. But I have been having difficulty attaining an erection during sex, and an equal difficulty in maintain what little I can come up with. During sex I have to maturbate to generate enough of an erection to penetrate. Then I have to penetrate fast and find sufficient stimulation to keep the erection. If I can accomplish all this, I can have a fairly ok experience, but it is not anywhere near what I used to be capable of. I can masturbate fairly successfuly. But it does take longer for me to generate an orgasm, and I can generate an adequate erection, but only if I use continuous stimulation. If I stop for more than a few moments, my erection will subside quickly. I have not been able to teach my partner to duplicate what I have can for myself. I do not respond hardly at all to her attempts to arouse me. In my present relationship, I am very attracted to and comfortable with my partner, and she is very understanding and accepting of the situation, so performance anxiety does not seem to account for my dysfunction, although that was my initial conclusion as to the reason for my problem. And my stress level is low right now also. I am scheduled to see my doctor to address my concerns, but I am curious to know if anyone can lend some possible insight so that I may be able to ask more specific questions of my doctor, as I am beginning to feel the cause is physiological. But I have not noticed any hair loss or other possible endocrine-related symptoms so far either. What could the above description most likely indicate is my problem?What could be the likely cause for my sexual dysfunction?
You need to seek a complete medical physical exam including blood %26amp; urine workups to determine what may be causing your issue. Please read the following article to see if ANY of the items listed apply to you. If they do - then some lifestyle changes could help you with your problem. If they don't - then definite medical evaluation is recommended.





What are my options?





Definite DON'Ts





Alcohol








Alcohol kills reproductive cells and decreases sperm viability. It also disrupts the link between the brain and the penis. Excessive use of alcohol inhibits the creation of the male sex hormone, androgen.





Smoking








Nicotine reduces arterial pressure and as a result, prevents blood circulation to the penis. In addition, toxic substances from smoking are detrimental for sperm maturation.





Marijuana








Sharply reduces the level of male sexual hormones, disrupts chromosomes and promotes undesired genetic changes.





Anabolic Steroids








Anabolic steroids bear a close resemblance to testosterone and as a result, the body stops its natural production causing impotence to occur.





High Cholesterol








Too much cholesterol blocks the vessels providing blood to the penis and thereby reduces the blood flow necessary to maintain an erection.





Overweight








Being overweight can disrupt your hormone balance and, as a result, the production of hormones necessary for achieving erection can become insufficient.





Chemical drugs








Studies show that out of two hundred most used medicines; as many as sixteen are likely to cause impotence. Among the most risky are drugs used for the treatment of high blood pressure, depression, insomnia, ulcers, tumors, plus a couple of medications used to combat allergy.What could be the likely cause for my sexual dysfunction?
high blood pressure, clogged arteries, stress, getting older like me, certain medicines like blood pressure can do it. my dr. got me straightened out though when he gave me some viagra. by the way i,am 60.