I know it's a hard conversation to have - I feel for you and I wish you luck!!!!!
I would try the old song - ac-cen-tuate the positive. e-lim-inate the negative. I find this works well - especially with men and kids (who aren't too far apart on the scale of not liking negative info!!!!!).
So I would have the conversation about going to the Dr and then tell him you were thinking about things that you really LIKE that he does WELL. And you and the DR thought that if he could do those things MORE it might help you - and then list a couple of the not-as-x-rated-stuff.
You said you have tried to re-direct him..... but maybe if you are re-directing him in a positive way rather than a "don't do that" way it might work?????
I found that if that my guy was doing xyz that I don't like I just looked at him and said "I LOVE it when you kiss my neck - could you do that?" followed by a couple "that feels really good". After I did that a couple times he ended up rarely doing the other thing and would go for the neck (sort of pavlovian, I think). But that depends on your tolerance for having it take a couple times.
I think you can also give him prefer over dislike - I like it when you rub my back more than when you kiss my ear.
If all else fails..... I think you can make it easier if you are up front about the fact that YOU have been embarrased to be honest about what does and doesn't please you. Again, I would focus on the positive, and maybe only pick the top 1 or 2 things that he does that you don't like as opposed to giving him a list.
And here's the controversial stuff - try to get YOURSELF 'in the mood' BEFORE you know you are going to be with him. Whatever it takes (and I do mean WHATEVER). [If you don't know what pleases you - now might be a good time to do some 'exploration' (if you know what I mean)]. If you can't do even that - that's OK, but maybe just thinking about something he did nice for you would make you feel better about being with him.
I hope you find an answer - intimacy is really really important in a relationship so I hope that he can help you.