Deepening intimacy with my husband/partner

I have been with my husband/partner for over 8 years now and we are good together in many ways. We talk especially well about concepts and intellectual subjects.

We have also talked about childhood, parents etc. He will also mention events that happened when out socialising with friends and is not afraid to talk about psychological motivations of a friend we know who is having relationship difficulties. He is very understanding of his deeper issues. So he is not emotionally illiterate as some people are.

But he never mentions his own past relationships, what he learnt, what sort of emotional journey he had. He can't even be straight with me about how many serious relationships he has had. And yet we are both old enough (mid-life) and wise enough to know that what happened in youth and up to our previous marriages (he even had children there who are grown up now)- and even since- are not a negative comment on our relationship now.

I tried to talk with him at times when we first got together, but he wouldn't let go of the idea that it was the past and that's that and started twisting it into some kind of character flaw I was exhibiting by asking! So I just left it and refrained from talking about my past relationships either and have done for the years since.

Yet I am certain he has nothing dreadful to hide. And it's a bit selective to detail past stuff with parents or friends but to literally never mention the girl/woman he was probably with at the time (and I know there are times he has said "when I was out" when I know dammed well from a previous time that it was "we"!

Now I am not wanting intimate details. I also have things I wouldn't want him to know and that should be respected as the intimacy of the time. But our past relationships shape who we are and I think to be able to mention about them, even just a little, in the light of learning and without condemnation should be part of a long-term committed relationship- especially marriage- particularly as neither of us are superficial characters and both have a deep interest in psychology and social issues.

As an example, I could mention a relationship I had where I realised the man didn't actually love me, how that affected me as a person at the time and how I grew from it without betraying the relationship or giving any details about the sex; but it would surely be enriching the intimacy of my marriage to share about my development. As it is, I don't even mention this aspect of my life development- why should I when he won't and I also know for a fact that if I venture into those waters, he will not reciprocate the intimacy and almost certainly flip into criticising my motives.

When I look back, we aren't sharing anymore intimacy in terms of who we are than we did in our first year together on this level, and maybe less actually! I find it very frustrating and I can feel myself starting to pull away inside, which affects everything and is stressful for me.

Can a relationship remain rich and intimate with such gaps?

Is it normal to want to share these things in a marriage (I know casual short-term relationships don't need this intimacy so please bear the difference in mind)?

Do any men out there know why he might be like this?