Stretchmarks

I felt like im getting depressed about my growing stretchmarks. I only had them this week! @ my 31 weeks and im getting obsesses by its appearance. Help me i feel like this will cause my postpartum after i give birth.. ??? Well since im super worried about it, my friend recommended me Bio oil, which is kinda pricey but she said its effective however im afraid that it might affect my growing fetus. She clearly stated that its fine for pregnant moms, but im STILL skeptical about it. Have anyone of you tried it or any suggestions??