Sorry long winded reply.
You would need to define 'nothing new' watching porn and what that baseline is?
As in my normal erection and loses stiffness very easily and then takes a few minutes to get hard again. I think it's stress related
I am assuming that means you get a reasonably good quality erection normally but can be difficult to maintain? In which case it is surprising you did not notice a difference?
The points about delayed absorption etc are all valid but as I said previously if you got a stuffy nose then the drug has been absorbed and working.
Solo masturbation can be a useful diagnostic tool, in that you are in control of most of the ingredients. The mental stimulation and arousal is being reinforced by the pornography (for most males) You are also in control of the physical /sensory/tactile component. You normally are isolated from any other factors ie another real person. As a result you should then now what is your ‘norm’ in terms of erections.
This can vary slightly for example depending on frequency of masturbation, porn content etc but everyone will generally know what is their baseline.
If you are over circa 40 and you have found the quality of your erections has gradually declined over time whilst masturbating there may be a physiological cause. In most instances this is just age or lifestyle related and could be described as normal, but could be a more serious cause (eg prostrate disease) The ‘morning wood’ test has been mentioned by others and this still remains a useful diagnostic tool also in terms of physiological causes.
In the solo situation you will usually have eliminated any effects due to performance anxiety. However whilst the brain is essential to the arousal process, it can also quickly interfere with it in the way of general stress/anxiety. See how quickly your erection disappears when someone opens the door unexpectedly!!
So yes your general mood will have a profound effect as you have suggested and only you will your personal state of mind? This will be most noticeable in having sex with another person involved, but can still affect the solo masturbation and I have experienced that.
Reasons for ED can be complex and often with multiple causes which then compound each other. Unless those causes are severe medication Sidenafil especially should improve matters.
As a general rule most people should start with 50mg and either reduce to 25mg or increase to 100mg dependent on results.