ED is not normal. If you have it something more than boredom is going on.For most in the 40 and under croud, ED is caused by overuse of internet porn.
Chronic use over years can cause severe ED. That said we have many guys in their teens and twenties on our forums with porn-induced ED. They get better with a period of abstinence.
Internet porn can become an addiction, and with all addictions the brain changes, or adapts. It does not matter if the addiction is to a substance or whether it is a behavioral addiction, the same brain changes result.
Today's internet porn is nothing at all like our ancestors ever encountered, with the constant novelty and genres of extreme porn. Unlike yesterday's Playboy, Internet porn overstimulates the brain structures responsible for libido, erections, and addiction.
Brain changes include a drop in dopamine receptors in the reward circuitry. Reducing the amount of dopamine receptors decreases your pleasure response to "normal" stimuli. In other words, real-life sexual partners and previous porn won't excite your brain enough to get your penis going. Turning on dopamine receptors is how you get turned on.
Here are two excellent presentations, by a science teacher, on the effects of pornography on the brain. They are non-religious, non-judgmental, and science based.
Erectile Dysfunction and Porn:
http://yourbrainonporn.com/erectile-dysfunction-and-porn
Your Brain on Porn - Porn Addiction:
http://yourbrainonporn.com/your-brain-on-porn-series
“How I Recovered from Porn-related Erectile Dysfunction”
http://yourbrainonporn.com/how-i-recovered-from-porn-related-erectile-dysfunction
As Porn Goes Up, Performance Goes Down?
http://yourbrainonporn.com/as-porn-goes-up-performance-goes-down
I believe that many ED problems can be attributed to "boredom", doing and trying the same thing again regardless how much you love the woman you are trying to please. It can lead to depression which will make the problems worse.
Solutions? Put some adventure in your lives, not necessarily sexual, but different places and things and the sex will follow.