So how do you get past the holding back, because I see this as a common problem?
Lou, My H had this as well (as you said it's very common)...what Heywyre's H just did...telling her (finally) and saying "I guess I should have told you that", is a step to getting past it. In my sitch with my H it's taken baby steps like this...where he'd finally say something, that yes...should have been said long ago, but he finally verbalized it nonetheless....and I made it safe for him to do so. I didn't chastize him by saying "Why didn't you tell me that before?!", I would just respond with something along the lines of "yes, that's exactly the type of thing I need for you to tell me. That's exactly the type of information that is helps me understand better...thanks for telling me."
I found with my H when I would take this approach...he would open up to me quicker. Not fast by any means as far as how quickly I would say something...but much faster than he had done in the past. Each time he would speak his mind quicker and in a less confrontational way.
So I guess my view on getting past this is....baby steps, encouragement, and validation of the effort when it happens.