This has been a fascinating thread, thanks to the OP and everyone else for the information you've put out. No doubt it will be useful to many. I had some minor problems a while back when I was in my late 20's.I could get hard enough to have sex but I knew I was far from my best form. I took Viagra and it helped a bit, mainly with getting me back up to 2 pops. However, I felt it only just about did the job. The second time I had problems was worse. I could just about get hard enough to have sex but I could not maintain it very long without starting to go soft. Also felt I was not getting up to my full length and girth either. Sex began to feel like a race against time. I got a prescription for Tadalafil. It worked like a dream. I was easily able to get a rock hard boner at full size which I could maintain throughout sex.I had no side effects either, maybe just being slightly more likely to have a headache a bit later on. I also found it really does last 36 hours too, maybe more. You do have to be careful, just the sight of a hot girl or a sexy thought during the 36 hours can produce a rampant and obvious hard on, which has the potential for embarrassment when out and about

. My partner at the time was not aware I was taking anything but commented appreciatively about how I was getting so much harder than I was before. It really improved things for both of us and gave me great confidence. In time I was able to stop taking it but would not hesitate to take it again if I needed.
I think ED is a problem that builds gradually. You start off able to be very hard and as time and unhealthy living progresses, your penis becomes softer. I think porn can also be problematic because it encourages the viewer to masturbate for periods which are longer than a decent erection can truly be maintained. The penis then becomes habituated to a below par level of rigidity which could progressively get worse.It also desensitizes the mind a bit too. Porn works by a process of amplification. You are not actually having sex, so the makers need to show stuff that is at a higher level of , for want of a better word - filth. This is not only to grab the attention of the viewer but to give them a sense of "yes this girl is well up for it, she'd definitely let me if I were there too." However all of this has the tendency to subtly shift our erectile reactions to the voyeuristic rather than actual sex.
The penis is rather like the rest of the body. Imagine running the 100m. You cannot maintain that speed and intensity over a marathon. The muscles will not perform to that same level. The penis is the same. Excessive porn and wanking will make it react as if it is involved in some kind of low intensity aerobic exercise and that will become the default setting unless steps are taken to break the cycle. I think the best way of doing this is to eat more healthily, ditch porn and even wanking if you can and to exercise sensibly. It can be difficult giving up an unhealthy diet but try building up gradually to 5 a day fruit and veg is the main thing. Doing it overnight can be a digestive shock. So many have said to cum only when having sex. I think this is the gold standard but perhaps not practical for everyone. If this is the case, keep porn and wanking to an absolute minimum and don't go longer than you would aim to last during sex. If you can avoid wanking completely it will give your penis so much more rigidity and energy. Add 90 minutes of moderate cardio to your weekly routine and maybe some work with free weights if you have the time but don't bother if this will make you tired and rundown.
As many have said, I think that underlying health issues are one of the main problems with ED. Despite being slim and healthy looking, I have often had a horrendous diet and lifestyle which on 2 occasions caused me problems. The second time I resolved to change things for good. At the end of the day, this is a health issue. Unless you are elderly, ED is probably a sign of some level of sub standard health. Not only will fixing the problem improve your sex life, it will improve your general health. And while you are sorting out your underlying health issues, don't feel embarrassed about seeking meds for your cock. For example if someone was getting medication for angina, nobody would say "Oh actually he has a really bad heart and deserves to have a heart attack because its only those tablets keeping him alive." If any other part of your body wasn't functioning, you would get that sorted, why should your cock be any different ? Hopefully the comments on this thread will encourage at least one person to take the steps needed to bring back their mojo and I can vouch for the fact that there are medicines out there that really work wonders