I'm 25 weeks no stretch marks *fingers crossed*. I use cocoa butter cream daily, especially after showering and if I'm itchy. Stretch marks can come at any time though, if you haven't yet I would use some type of moisturizer or cream daily. And as mentioned above drink plenty of water.
You can get stretch marks at any point in pregnancy. Because your skin is stretching to accommodate bub, this is why you get stretch marks. Some people don't get any and others can can them anywhere and everywhere.
I'm 25 weeks and have them on my inner thighs, hips and butt when I've never had stretch marks before.
It also comes down to the elasticity of your skin. To help increase the elasticity, you can eat lots of greens, drink plenty of water and use a thick/rich moisturiser daily :)