How can you be a lawyer if you can't handle a bit of conflict?
It's the effects of coercive control and it can happen to the strongest of people. OP it's not your fault and it doesn't make you weak.
I decorated a truly awful bathroom once, pain peeling off the wall type awful. I like to take a bath and it annoyed me so much. I said to my partner "I've saved up £50, ok if I decorate the bathroom?" He said no problem and I got on with it. The ONLY reason I asked permission was because it was his house and I didn't live there!
You have a right to need things. You have a right to want things. Obviously in a marriage there has to be some discussion and if necessary some compromising. But not justifying. You're having to justify every single thing you want (and need?) and obtain his permission, otherwise you can't have it. That's financial abuse/emotional abuse.
In your situation I'd do something that I think is necessary whether you split or stay together. Open a bank account in your name only and get your wages paid in there.
Work out the total cost of household expenses for daily life, which includes children-related expenses.
Work out what percentage your wages are of the joint income. Let's say it works out at 30% of the total joint income. So you transfer 30% of the household expenses amount into the joint account as your contribution to the running costs of life.
Open a savings account in your sole name. Put a bit aside if you want to each month, maybe for a holiday or an escape fund
Spend the rest on whatever you like. Family day out? New shoes that you don't need because you've already got loads? Something for the house? A car? Anything at all. You've every right to.
Tell him what you've arranged with the new bank account, your wages going in there, your contribution towards the household expenses. Tell him it's because you felt you had no control over anything.
If his response is anything other than "oh right, no worries, that's fine", you've got a massive problem (in the form of a controlling prick for a husband). It's totally fair, totally reasonable and you shouldn't have to justify yourself at all. It should cause no argument, no conflict. Because if he's not controlling you then what has he lost?
If it's an accident, him feeling he's got final say, because maybe he's never stopped to think about it, making this change to the money situation will make him aware of it and make it clear that you have rights too. You shouldn't hear another peep out of him about your spending choices.
If it's financial abuse then by you doing this he's just lost control and is likely to get angry, sulk, give you silent treatment, stop doing his share of chores, or try to "punish" you in some other way. It might take the form of him going on and on and on and on at you endlessly, about how "unfair" you are, how you should reverse your decision, how he didn't get a say in it etc. All to try to grind you down and get you to comply with his wishes.
Be aware that if it's emotional abuse he might not say much, or anything, about the changes to the situation, but the expectations that you'll justify every purchase and get his permission will continue. Even though you've paid your way and it's your money, that you've earned, sitting in your bank account. So he could start to "punish" you, as above, when you stop doing that. Watch out for endless questions about why you've bought xyz or little digs/insults for having done so.