Wicked Wanda, your post is awesome. I sat here for awhile thinking how to answer this in some helpful way. For me, I kind of have a logical look at it - it's just body fluid, part of my lover, and no more dirty or gross than my vaginal wetness that I want him to get his tongue into.

I agree with Wanda that the problem sounds much more psychological than physiologic - your issue sounds to be more with the idea of cum in your mouth than it is with the actual taste or texture of it. It may be easiest to start off trying to think of it as something other than cum - ie, a mental trick that it is milkshake or something yummy. I don't know if this will help or not. Hope it does!

Lastly, if you just can't get past it, it's no big deal! There are so many ways to have fun with your lover, you can definitely work around this one thing! Everyone has one or two things they just don't want to do (for me, it's anal - I tried it once and wanted to crawl up the wall as soon as he started). I'm sure your husband is a happy camper and probably thrilled that you're making such an effort for him.