SOS ( Please help) Due to this problem.

I am 34 years old, and I weigh 115 kgs. I have tried having sex a few times. but in vain. I checked with my family doctor who advised me to undergo hormone tests. It was found that the testerostone levels are too low. It was shocking to know that the readings was looking as if it's done for 16 years old juvenile. Doctor also advised me that it's a birth defect and nothing can be done about that and also requested me not to get married. I am not getting erection at all. I am able to do mastrubration but most of the times my penis is semi erected. The amount of semen too is low.. sometimes it's watery and not white... Could anything be done at all. Also please advise on hormone replacement theraphy. Does it come with side effects. Am very very worried about my future. All of my 3 previous relationships have been turned down due to this problem..