Stretch marks

So I’ve been really concerned lately because I’m staring to get a lot of stretch marks on my belly, A little under my belly, to my belly button. I’ve always had stretch marks ever since I was a kid. It never concerned me until now. I was never over weight until now. If I decided to lose weight will they start sagging or look saggy when I lose it? I don’t weight over 170 pounds, but will get there if I don’t decide to lose it now. I am also a little bit short at least 4’11”