If you gain OR lose weight pretty quickly, stretch marks are to be expected. I gained 40 pounds in six months, not a stretch mark in sight. Then lost 10 within two months, and the entirety of my thighs were covered in them. Even the top muscley bit. Not just the jiggle room between them
The only posts I've made in this forum so far have all been about BIO OIL because it's magic, and so many people ask about stretch marks. It's what I use. The marks on the tops of my thighs are completely gone, I'm just waiting for the rest to keep fading away. But you'll see results by day three of using it. You can get it at walgreens.com. It's pretty expensive, (12 dollars for two ounces, I believe) but my two ounce container has lasted me a month, and still isn't empty. A little goes a very long way.
Good luck!