have encountered this problem before, here are my 2 cents:
(1.) morning erection upon waking means you are not impotent, but you still can get ED.
(2.) ED have 2 causes, either physical or psychological.
(3.) If you are finding hookers, you are presumably not married, which means you could be watching lots of porn and masturbating...then when it comes to real people you get "sian" (becos always using your hand) and you cant perform. Porn is no good, neither is reliant on the hand, try to do it only once a month, no more.
(4.) If you are married or attached, your other half may be either a cold fish or very dominant in bed...that means she only care about her orgasm and does not want to do any work(one dead position), hence you become fearful of sex with a woman, and repeat step (3.) and get psychological ED.
(5.) Do you have injuries near the groin/pelvic area? sometimes the nerve may be injured, e.g. constant weight lifting, running, cycling...you can try physio (very expensive) or TCM (acupuncture) to give the nerve relieve, esp the pedundal nerve...
(6.) what is your cholestrol level? If it is very high try to lose weight and change diet only to fish, vegetables and anything that is not deep fried(preferably steam). Go vegetarian only on certain days. To lose weight effectively, have green tea and apples everyday...really works. Losing weight also helps improve your image, gives better confidence to both yourself and the female party...
(7.) If you are rich, you can also try cordyceps. Take it for 3-6 months and see the effect. No money then take the pills form...Horny goat weed only increase nitric oxide temporary, may or may not work for eveyone as the ichrin amount in legal doses is not very concentrated in singapore...
(8.) If frequent urination or blood in urine, pain upon urine, incontinence, better go polyclinic get referral letter to see urologist...If nerve affected and prefer western medicine, can also see a neurologist.
(9.) exercise a lot (see diet), about 2 hours a day, in both cardio and weight lifting (free weights, sit on a chair, dont stand). exercise helps circulate blood and releases endorphin, helps overall well being a lot.
(10.) Foods with aphrodisiac properties: chocolate, watermelon, banana, fish, etc...
(11.) If all else fails (you feel you are near impotent and porn dosent help), better go check if you have diabetes...it is the mother of all fuckups and leads to many other illnesses...