HELP!: Stretch Marks

I've tried everything I can think of. I started using Burt's Bees Mama Bee belly butter once daily as soon as I found out I was pregnant. When I got into the second trimester, I used it twice a day - religiously. In my third trimester, I started getting stretch marks. I was still using the belly butter, then switched to Bio Oil and Cocoa butter twice, if not three times, daily. Now, at 36 weeks, my belly is covered in tiger stripes. What am I doing wrong?! Is there anything that can help this?