Have you had or considered counselling alone and as part of a couple?
I am interested in the bit you said earlier about the lies being about self preservation? What do you mean by that?
I think for you, you need to accept that sometimes decisions will be made with out you. Sometimes decisions need to be made there and then. In which case, if this person is truly a partner, you would accept they made the beats decision at the time.
For example dh was asked if dd wanted to compete for the first time in a sport she participates in. He tried calling me and I missed it. We had been away and it was closing day for entered. He decides to enter her. I wasn't happy as its a contact sport and thought she needed more training. But I also trust that he did the best thing he could at the time.
Dd performed above everyone's expectations, so my thought that she wasn't ready was wrong.
I know this is an odd example. But what I am saying is in a fairly normal relationship you should be able to trusts that your partner has made a decision and made the best one they can at that time.
It sounds like you are in a circle of your partner lying about something small, you make situations worse than they need to be, you get upset and start 'worst case' thinking, the partner then lies again to avoid this behaviour from you. And round you go?
You are both stuck in the cycle or poor behaviour and neither are happy.
And it's not got to a point that it's so bad and gone on or so long it doesn't really matter who started it.
Is this about right?