I would imagine you are concerned some of those old behaviors are showing them self again, the controlling behavior- I would imagine part of the reason you divorced him in the first place.
Your husband may have the best intentions to "change", and may have professed this when you remarried. He may be falling back into the old ways of again controlling.
What you describe is a double standard, he seems to think he has separate and different rules for himself, and you. That is not equality in your relationship.
Often times people initially lie to "avoid" a conflict or confrontation, however, lies become difficult to keep track of and maintain. Might he have originally not told you of the contact with ex to avoid a fight or to avoid hurting you? He may be trying to "please" two women in a sense, and or avoid angering both women. You need to be his priority in this vs. his ex. His children, of course are important, but the way he is acting his putting a wedge between the two of you.
Like you said being the "last" to know is hurtful and embarrassing to you. It is disrespectful that he is not negotiating this with you, compromising to make it more equal ground for both of you.
Do you worry he's becoming that man you divorced? He's lying about other things... This becomes more difficult to know when and if he is being honest. He becomes annoyed when you have contact with ex. It is unhealthy in your relationship two have two separate sets of rules.
I would encourage you to set up a time to talk to him more openly about your feelings. Maybe writing down your feelings before, help you sort out what you want to say. Try using the "I feel...when...and I want..." verses the "You lie, you never, you always..." The I tends to lessen the defensiveness in the other person. If we own our emotions verses accuse, the other person may be more apt. to listen. Finding a time, other than when either of you are upset would be best.
Because there is that history of conflict and divorce some unresolved stuff may be showing up.
Have the two of you done any marital counseling?
any additional comments or questions to what I posted.