I started seeing them around 32 weeks, but only on my sides, above my hip bones. I still have the marks, but they've migrated toward my back, so I don't actually see them unless I use a mirror. I don't have any on my stomach, just wrinkly twin skin that starts at about my bikini line. Like PP said, my belly button will never be the same, glad I stopped wearing the navel ring years ago!
I didn't try any anti-stretch mark creams, as everything I used for itching tended to make me itch worse. It's funny thinking about it now, it seems like a lifetime ago.
Nikki, mama to DD and DS1 (6/07) and DS2 (10/10)