Hello,
Stretch marks are mainly due to sudden weight loss after massive weight gain. other causes can be any diseases which affects elasticity of your skin, prolonged usage of steroids and hormonal disturbances as indirect cause
Stretch marks can be treated by micro needling and fractional co2 lasers. Even stretch peels work but the results are not 100% and multiple sessions required
Next Steps
If you further want to know about treatment options then kindly consult me online via practo pro