You could be having ED due to a functional/mechanical problem, due to compromised blood flow, due to many different physical conditions - if it is not a unique performance issue (and it sounds like it's not).  A urologist can do the necessary tests to begin a workup of the causes of the situation - just make sure to preface when you get a referral or make an appointment - telling them specifically why you need the evaluation.  some urologists specialize in this area and sounds like you would benefit from that type of urology specialist. Please also check out my blogs which can give you some insight as well.