Seeking expert testimony is a sign of strength. A personal relationship with a caring professional is proven clinically effective.
I believe that I can help. I like your idea of keeping a journal and using honesty even when it "makes you look bad". Honesty, even if you have to be humbled, does not make you look bad but makes you look better. Honesty can make you look great, in fact.
You cannot, of course, just tell him to trust ou again, especially when that trust has been damaged. Your actions must speak louder than our words and you must walk the walk, every day.
You may have to give up some of your privacy in order to be more open to him, so that he can see that you are authentic and not hiding anything.
Continue your new policy of truth-telling, whether he approves of what you have to tell him or not. At least he will believe what you say.
Don't keep any more secrets from him. They are so hard to cover up and they always come out in the end, making things worse.
Reveal some of your inner workings to your partner so that he feels safe with you, and that you are predictable. Let him know when you are tired, or don't comprehend something (not just about him), or if you are feeling down, or anxious. Let hims know how you think and work. Sometimes you will need alone space and he will need to back off.
Listen to him carefully and see what he likes and how he likes to do things. You dont have to do things either his way or yours, but you should both understand each other's emotional needs and preferences. If you don't know, don't be afraid to ask him.
You don't always have to agree, but if you both try to communicate and are interested in what each needs, then you will build a loving trust based on consideration and mutal regard.
Finally, let me recommend a wonderful book that will help you a great deal and be a positive influence on your life:
I wish you great fortune and success.
Elliott, MAE, LPCC, NCC, CCMHC