erection-problems

ERECTION PROBLEMS
An erection problem is the inability to get or maintain an erection that is firm enough for a man to have satisfactory intercourse. You may be unable to get an erection at all, or you may lose the erection during intercourse before you are ready. If the condition persists, the medical term is erectile dysfunction.

Considerations

Erection problems are common in adult men. In fact, almost all men experience occasional difficulty getting or maintaining an erection. In many cases, it is a temporary condition that will go away with little or no treatment. In other cases, it can be an ongoing problem that can damage a man's self esteem and harm his relationship with his partner, and thus requires treatment.

If you have difficulty having or keeping an erection more than 25% of the time, it is considered a problem.

In the past, erection problems were thought to be "all in the man's mind." Men often were given unhelpful advice such as "don't worry" or "just relax and it will take care of itself." Today, doctors believe that when the problem is not temporary or does not go away on its own, physical factors are often the cause.

One way to know if the cause is physical or psychologic is to determine if you are having nighttime erections. Normally, men have 3 to 5 erections per night, each lasting up to 30 minutes. Your doctor can explain a test to find out if you are having the normal number of nighttime erections.

Source
http://www.nlm.nih.gov/medlineplus/ency/article/003164.htm