I haven't heard of dryness alone causing stretch marks, not without some weight gain/loss. It could be that if you were not hydrating well and gained weight, or height, that the skin would be stretched more rapidly without the elasticity from moisture to ease the stretching. Or, you could have gotten these when you were going through a teen growth spurt and because of their location you just didn't notice them before.
Once a stretch mark has gone white there is nothing you can do for it short of laser, and I don't recommend that either. I've seen a few cases where the effects of the laser were uglier than the stretch marks had been, and personally I don't think it's worth the risk for something so minor. Like Tony said, guys really just don't care about them. There area lot of creams out there that claim to reverse them, but I didn't start trying any until mine were already old, so no luck there for me. By the way, Strivectin, the market leader in this catagory which is also used on the face to fight aging, burned the heck out of my face and didn't work on my old stretch marks. I have heard some women rave about it working on red stretch marks though. I just self tan over them, and that helps to minimize their appearance.
The best thing you can do is prevent them in the first place. Use a deep hydrator, like Bag Balm, the Cocoa Butter from the Body Shop or vitamin E oil often during pregnancy, weight gain or weight loss. Any time you feel itchy, rub it in, as scratching will irritate the skin and some derms say scratching will accelerate stretch marks. Deep hydration will make the skin more supple, allowing it to expand and retract easier and preventing skin tears (stretch marks).
Unfortunately, a lot of what determines whether you'll get stretch marks or not is your genetics. If your mother has them, chances are you will too. I have fewer than my mom, but I did a lot of deep hydration and she didn't, which could have helped to prevent me from getting as many as she did.