Forms behavior with browser navigation

I have a case with a flow im designing that is very rare, but i need to solve it anyway. I describe you the scenario. In a credit card form, the user inserts all the textfields, when he clicks the submit button, it validates all the textfields and goes to the next screen. Then maybe he wants to go back with the back button from the browser navigation, because wants to change some information. So once he changes the info in the textfiled, instead of validating the textarea with the submit button, the user uses the forward button from the browser navigation, and goes to the next screen (without validating the info entered in the textfield). Now it comes the problem: If the user wants to go back to the previous screen, what should the user expects to finds? the last text entered, that maybe it was uncorrect, because it wasnt validated? or the last correct text entered by the user using the submit button. I hope u could help me, because the step of entering confidencial information such as a credit card is a really pain point for a user.