Yea, I've been to the doctor, as have many others. Seen 2 endos, a uro, and 4 GPs. None have any explanation, although one endo said he's seen this before in a few other guys before me. They tend to just give you a RX for v**** and cialis and send you on your way. But that's just a band-aid, it doesn't help with libido -- which is hormonal, and something the drug interferes with.
Problem is most docs don't recognize a decimated sex drive and lowered T levels as a possible outcome of using finasteride... because it's not well-known (yet). However, there are doctors, such as Dr. Eugene Shippen, author of the Testosterone Syndrome, who has treated a number of men with these issues post-finasteride and claims to have had some success in helping them recover via further treatments to boost endogeneous Testosterone, reduce Estradiol, Prolactin, SHBG, or other imbalances post-finasteride.
All the info is in the FAQ on propeciahelp.com if you've haven't read it.
And your Estradiol level should optimally be between 20-30... consider getting some DIM supplements, and eating a ton of brocolli to help with Estrogen metabolism. What are your side effects, anyway?