stretch marks and saggy skin am I doomed forever

tammymusic1

I have had 4 kids and went from 108lbs to 210 by the time I had my fourth. I yoyoed 30lbs up and down for 6years then in march of 2012 when I realized I had hit the 200 mark again I decided to get serious. In the last 14 months I have gone from 200 down to 124.5lbs But I have crazy stretch marks all over my tummy area and some saggy skin I notice how bad the saggy is when I was doing planks today . Will these just be something I have to live with forever or is there a way to tighten up the skin and help the stretch marks at least lighten.