Advice on stretch marks?

I'm really confused about the concept of stretch marks. I have some on like the lower side of my hip like my butt that first appeared about 4 years ago.

I am by no means overweight or even remotely heavy. I'm 5 foot 1 and weight 90 pounds. I'm not terribly insecure about them. The only time you can really see them is if I wear bikini bottoms that show like EVERYTHING, which I don't.

I know they have to do with growing and skin stretching stuff, but I've always been pretty thin and haven't put on a large amount of weight at any one time?

From anyone with experience or knowledge, is there anything that will help them? Will they fade more over time?
Advice on stretch marks?
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