How old are you?
I think if you are legitimately lacking in testosterone, there may be a medical problem that is at play? I am not that educated on the matter, but if I wasn't driven at all to sex with my girlfriend, and felt no drive whatsoever, I would assume larger problems, and supplementation wouldnt be my first course of action.
If I ever feel lethargic or apathetic, an intense weight lifting session followed by some hard running generally gets me harder than Clint eastwood in dirty harry, besides giving me more energy, stamina, drive, ambition, etc.
Have you seen a doctor about this issue?