Welcome to the BB....as you can see you aren't alone, there are other HD women on here as well, myself included.
I have one thing to say right now though, and I hope you are already thinking along this line. DO NOT MARRY HIM UNTIL THIS IS WORKED OUT, if it's worked out. This is a problem that won't just go away....some beat it, some don't. But don't marry him thinking that this will simply change....it won't. If it changes it's going to take a lot of hard work, and he's going to have to be willing to make some big changes (and you too possibly) as well.
It's a great thing that he's at the very least willing to read SSM. It's also good that you two do seem to be communicating.
Have you told him how all of this makes you feel inside? My H also always let(s) me do the majority of the work when it comes to any form of intimacy between us. I have had to no-holds-barred tell him how horrible it makes me feel to feel unwanted and by that I mean I have to say. "I feel...unattractive to you, I feel unimportant, my self-esteem is affected etc.
Let me ask you this...you say he's agreed to work on the problem. What, other than reading SSM is he doing in order to work on this with you? Has he agreed to a C? Have you both thought about seeing a MC together? Also, you said he's agreed to seeing a Dr.....he hasn't made the appointment yet? My H did this too.....it was as if agreeing to see the Dr. should have placated me, but when it came down to it....I had to tell him he either needed to call and make the appt, or I was going to.
Also, there a concept called boundaries and consequences you need to begin becoming very familiar with. What will be the consequences if things don't change in this area of your R? You need to communicate clearly to him exactly what you need of him and hold to it....then if things don't change you need to be willing to reinforce the consquences (whatever they may be fore you.)
Once again, welcome to the club none of us wants to belong to. You'll find many understanding people here....many of them are very wise and have great insight to share with you....they can also be a tremendous support system.