You and he are caught in a vicious feedback loop, and need to get some counseling help in communicating with each other. At the very least, it sounds like you need to learn how to better remain calm. He needs to learn to be more trusting of you, and grow enough of a pair that he's not in constant fear of setting you off (my guess is that in other aspects of his life he's also a procastinator and somewhat timid when it comes to tackling a hard or unpleasant task)
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I agree that counseling (especially in communication skills) can be valuable to make sure you're both on the same page.
Is it possible that your husband's birth-family experiences taught him it's not a good idea (or safe) to tell the truth, even to those you love? Might he have been severly criticized or even punished about small things he did (or didn't do) in addition to big things when he was young? If so, he may have unknowingly developed a life-long habit of telling "white lies" to protect himself and truly doesn't understand how frustrating this is for you as his marriage partner.
This is not an excuse for his lies -- but it may indicate that helping him break the old habit and create a new one would be a good idea for you to try out. If you aren't yet doing this, you can start by just being appreciative and complimentary when he tells you the truth instead of a lie, even about small things. If he's used to receiving painful criticism or anger from his childhood experiences, it's no wonder that he unconsciously wants to avoid this. It is obviously not easy for you to remain calm when you find out he's lied, but it reinforces his ingrained fears and his strong desire to avoid this response. This approach may feel like "training" a pet (or toddler) -- and it kind of is -- but the results can be worthwhile.
Helping him change automatic patterns is not easy unless he also truly wants this uncomfortable dynamic between you to be different. That's where professional support via counseling could help you start closing this communication gap.
If you love him and this "old habit" of his is not a marital deal-breaker for you, make time to talk to him about this when you're both calm and things are good between you. Help him understand how frustrating it is for you and how much you dislike freaking out, which is hard for you to avoid when you discover another lie. If he cares how important the truth is to you, it could help him begin to "risk" telling the truth despite his fear that you'll freak out. So when you DON'T freak out -- which you won't, right, even if you don't like the truth he's telling you! -- it can literally change his expectations of what might happen when he doesn't tell a protective lie, at least to you.
This shift in your relationship dynamic requires attention and commitment from both of you. But if he can't just "grow a pair" on his own, consider how you can help him "do the right thing" and get more comfortable telling the truth until it becomes second nature for him.
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It's simple, whenever someone lies to us, it is our fault. People lie because they are afraid of how the other person will react. When someone tells us the truth about something and we react emotionally or with blame and judgment, it sets the stage for them to lie in the future, in order to protect themselves. You want your husband to stop lying, then you must stop judging and re-acting. It's that simple. Tell him, "I want to stop this cycle that we are in, and I have decided to take responsibility for my part in it. I will not re-act negatively to anything that you tell me, even if I have found out that you have previously lied. I will not judge you or judge what you say. I will be open, loving and available to talk about anything that we need to discuss. It will be your choice if you decide to tell me the truth, and I hope you do because that can only lead to a better relationship." I even did this my 3 boys - they are now teens and adults and they always share the truth. It works!
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