some men have a "fix it" thing, where if their women tell them something that's bothering them, something they wonder about, no matter how innocently or idly, they think they have to "fix it". my husband gets super frustrated with me when i try to "vent" or "confide" in him, he doesn't understand why i just don't tell suzi q to shove it when she gets on my nerves at work (or whatever). and since he can't fix it and i "won't" (in his eyes), he gets frustrated. sure in a perfect world our men would be our bff's and we'd share all of our deepest darkest secrets and every little thought that enters our head...but....
in my experience, this is one of those areas where we do NOT need to be "completely honest".
it's who he is. let it go and try to find someone else to vent to. we all need it, i would just rely on hubby a little less for that kind of support :)
PS that's not to say don't discuss it with him. by all means let him know that it hurts your feelings when he blurts things out that were meant to be private. just don't be shocked if he doesn't get it, and don't expect his habits to change, even if he wants to.