The fact that he's already considering divorce means he doesn't know what marriage is. Sure, it's real it could happen, but it doesn't sound like she's the right one, or like he's ready for marriage, if he's not willing to tell her all his secrets! And thus, he's considering lying to her, because withholding is a type of lie, and thus will have set up the marriage to fail from the beginning.

So, yeah, maybe figure out what marriage really is before considering getting married and keeping lies.