Stretch Mark remedys from moms.

Iam going on 18 weeks pregnant and im getting pretty big but no stretch marks yet, just on my upper thighs where ive always had them and on my but there not noticable, im worried about getting the purple stretch marks all over my belly, ive been using palmers cocoa er for stretch marks with collagen and elastin to prepare my belly too stretch and afterwards i plan on using bio oil if i do have stretch marks, do any moms with experience with stretch marks have a remedy for them.? thanks for any advice!