As I was reading your post, I had to double check to make sure it wasn't my wife posting this message! I can relate to what your bf is experiencing; the low libido, the frustrations, etc.
I'm not going to pretend I can speak on behalf of your bf, but maybe it will be helpful to get perspective from someone who is experiencing something similar.
I experienced a lot of frustration whenever this was the topic of conversation. With help from my wife, she was able to get me to open up, not only to her but more importantly she got me to open up with myself. She was very patient with me, and was always clear on her intent <this was key for me>, which wasn't to complain but to explore and to discover. This helped tremendously since it lead me to self-exploration and self-discovery about this subject. You did say your bf is emotional and opens up to you, but this particular subject may be uncomfortable for him to talk about. This goes back to what EasyNow said about creating a safe/comfortable emotional environment for the both of you to talk. Taking that a half step further, make it a safe/comfortable emotional environment for this particular topic.
Easynow had other strong points about "fear of his own power as a man, anxiety performance, burried resentment," etc etc. The human psyche is something worth exploring and in understanding it comes the realization of the vast influence it has on everything. The hard part of dealing with the psyche, is it seems so subtle and in the beginning it's hard to distinguish the psyche from all the noise surrounding it. It also takes a lot of honesty, with each other and ones self before one can begin to perceive it.
I also agree with Pietro, I have realized there is some type of disconnect with the body. The pleasure is more in the mind than with the body for me. I'm trying to figure out how to overcome something like this, if it's even possible.
Also, I would like to explore what Song Yongdao had to say, "A rather Yin guy huh?". I'm exactly as he/she described... tight neck/shoulders, sporadic eating patterns. For me at least, this returns back to the idea of energy. In my mulling's over energy, one begins to see that maybe one's energy and one's psyche are indistinguishable. Which then begs the question, does healing of one of them inherently mean you are healing the other? Perhaps (this probably should be discussed in different post).
Well, hope this helps you and your bf!