I was going to write you a long reply, since I am 25 and have fought a battle with ED problems, but I decided to just give the short and simple reply.
I had a very limp cock until I started doing jelqs, so make sure you are performing those regularly. Also give up looking at porn and all sexy pictures, and give up masturbating for pleasure completely.
If you keep your eyes and thoughts off of sexy pictures for a long period, when you finally get with a girl and see any of her body, you will have an uncontrollable erection and desire. This is my secret weapon and it allows me to enjoy sexual things almost as much as I did when I was 13.
I set the rule that I would only masturbate if it was for the purpose of PE and stop the moment it was no longer necessary to perform my PE routines, which works well, but I always find it a struggle to control myself once I start masturbating for any reason.
I have just switched my PE routine to pumping and jelqs only for the purpose of having maximum EQ and horniness. I was clamping before which required me to stimulate myself too much so I dropped it since I could do a pumping routine and never have to masturbate. For jelqs I only have to stimulate myself for a brief second and then jelq, which is not too bad.
Through my efforts I have went from being able to look at the most hardcore pornography and not getting an erection, to just poking my cock and it starts to fill with blood.
I also try to limit my sexual encounters with females, instead of having sex 5 times every day with my girl friend and getting bored mentally. It is tough for me, but when I think about how rewarding it is to control myself I gain the will power to resist.
You should also do the obvious, which is eat real food and stay physically fit, as well as getting enough sleep and sunlight every day.
Another recommendation that I just remembered is if you are circumcised by the modern Periah method, do foreskin restoration a bit or find a synthetic solution. This helps as well, I have used Glad Press n’ Seal Wrap for this before and it worked, but I mostly use a silicone sleeve that I cut to cover just my glans.
I make sure to not let the synthetic foreskin hang over the end of my glans though so I am still like someone who is circumcised, I do not want to break the commandment to be circumcised from the scriptures so I do this to be safe.