Great Job on the 12 lbs! That is quite an acheivement.
I don't know about the stretch marks but those purple veins sound like vericose veins. I have a couple on my legs. I'm told that it is from standing/sitting a lot and that the best way to help them is to exercise. So we'll see.
I'm not advocating this, however, there is a laser surgery available where you can get spider veins zapped away. I've never done it or know anyone who has so I don't know what it's all about but it's available. You may want to consult with you family physician regarding these changes in your body as they may indicate something more serious going on.