Things to look at first like, Am I heathy, Am I overweight, If you smoke, are you smoking to much, Alcohol, am I drinking to much, if you have to many yes's then you need to get control of them.
Then try reading up about DHEA, its a over the counter hormon replacmet, but please read all about it first and its side effects, just put in the old serch engine DHEA for ED, or try looking up webmd and they have and page on DHEA, ie what it is, what it can do nad how much to take, I'm 64 and it worked for me, but I did read all about befroe going down the street with it.
Good luck
Go see a urologist. Only a doctor can determine the exact cause of your problem and prescribe you the right treatment.