It can be maddening when you start thinking that you "could" have handled a past situation better, and maybe, just maybe, you wouldn't have lost someone you loved. But this is just wishful thinking. We don't know what could have been. What we do know is that relationships that are meant to be, usually endure the crap that inevitably happens to them.
No relationship can be without problems. But sometimes these problems get out of hand, or become too much for two people to be together happily. Love just isn't enough for a relationship to work.
You went through a divorce for a reason. Analyze those reasons and make your peace with it. Like you said, you never really grieved the loss of your marriage.
If you require some space, you could talk abt it with your husband and explain to him that you need some time to sort yourself out because he might be hurt by your change in mood and behavior.
Cry. Let yourself feel everything. Slowly you will come to accept that it is over.
And you'll start to realize how you actually feel abt your ex and your husband. It need not necessarily be all bad. It could turn out that you do love your husband and that you are over your ex. But whatever it may be, you need time to figure it out - but don't take time to think abt who you love, but rather abt what hurts you