It's too late to prevent stretch marks. Stretch marks are caused when you gain the weight, not when you lose it. For a few people, the ones they have become more visible with weight loss, but for 99% of us, we just notice them because we're looking at ourselves more.
Sagging skin tightens up with time. A lot of times, what people call "loose skin" is actually the last layer of excess fat, and it goes away as you get closer to a healthy weight. If you were 50 or more pounds overweight, then you might actually have some excess skin. Whether that tightens up depends more on genetics and age than anything else. The younger you are, the better chance that your skin will go back to normal, but it takes some luck as well. The best way to reduce your chances of stretched skin is to lose weight relatively slowly-- if you drop 100 pounds in 6 month, you're pretty much guaranteed to have some permanent effect, but if you lose 50 in a year, it's less likely.
Either way, it doesn't make sense to worry about it now. It takes roughly a year *after* you've finished losing weight to know whether your skin is going to go back to normal.
| current weight: 132.0