I used cocoa butter too, it smelt lovely and I religiously slathered it on ever evening.
Didn't see a single stretch mark right up til the day my daughter was born - so would have sworn by it.
The day after she was born, I discovered my stomach was a blamange and at sometime during the night before, some evil old farmer had driven his plough truck over the whole of the underside of my belly I was fractured to bits!
Moral of the story, don't let farmers in maternity wards.
AND check underside of tum, that's where most of the weight is carried so most likely to stretch.
I even got stretch marks when I was a teenager when my hip bones grew, so really it's probably the luck of the type of skin you have.
Sorry I have no secret remedy or solution.
If you have ever watched Shirley Valentine, there's always some greek guy happy to kiss them. lol