Hi Javid, ED and its causes are great, but it could be stress,aneiety, and any meds you are on ie heart or blood pressure or even diabetes.
But some things, simple things you could try are Cayenne, Garlic and Ginger.
OK the Cayenne mix in tomato paste and thin with olive oil, mix to a heat that suits you, this you take 3 small spoonfuls 3 times a day, the Garlic a whole head and cloves chopped very fine, again mix with olive oil, and take the same 3x3 as above, wash both down with water, and take on alternate days, and last the Ginger this I keep in the freezer, grate down a pile to the size of a large egg, put in a mug with a slice if lemon, either micro wave 30 sec or just add tea black or green, green is best for ED, add some honey, all the Cayenne, Garlic, Ginger, and the Green tea are all good for your blood and its flow down below and all should help with your erections, you can google them for more info, just add ED to them.
With this you could either try some Tribulus a herb ,or some DHEA a hormon, the DHEA you read up about, as it can have some funny side effects with the odd person, and they both will help with your testosterone, boost your libido and energy levels.
Look Iknow you say your testosterone is OK, but these are both well known help for ED.
The Tribulus takes around 8 weeks to get to full power, and start the DHEA low, 25mgs and buld it up to what you think suits you, and after the 8 weeks cut both down to 5 days out of 7, the reson for this if you keep taken 7 days a week, then they wont work the way we want them to, OK
Good Luck
Do you have any medical conditions?
Do you masturbate too much?