That doesn't mean you need to get all alarmed about it, it may fall within a normal spread of human experience. But it would be best to find out why. If there were no traumatic events just preceding this (a death in the family, losing your job, something stressful or anxiety-provoking like that), you might need to rule out medical problems like diabetes or multiple sclerosis.
There is a good book on libido discussed on this thread.
Here is a page on erectile dysfunction.


