Hi,
I think, if he was earlier sharing his financial details and showing his payslips to you then he should be having no problem doing it now. I mean, what is the problem now? After having his baby and SAHM, you haven't become a stranger to him. After all you gave up your job for the baby , which is not just yours.
See, there is no issue if he would not show his payslips to you, but here, in your case, his not showing them now only is a bone of contention because he was showing it to you earlier.
I guess, speak to him, and ask him why he has suddenly become so secretive. Why has his attitude changed after your leaving the job? You must sit and clear things out as it is bothering you. Yes, you are right, you are partners and you must be open to each other.
Magbasa pa