Stretch marks ?

I’m a ftm and I have always been “tiny” not weighing more then 110 pounds I was 101 before getting pregnant , my belly isn’t huge but I definitely already popped I only have stretch marks on my boobs I haven’t had any on my stomach or anything ? Is there people who didn’t get stretch marks with there first ? I haven’t used anything to not get them I’m just wondering if they will come or not ? When did they start to come for you ? I’m 34 weeks btw.