I'd stick with Vitamin E. There is also something you can use called Oxsoralen or Trisoralen (both are in the psoralen family) it's used in atopic dermatitus and vitiligo.
It cuases the skin to thicken and become more even when exposed to UV light which makes it a great Rx tanning pill too. Dan Duchaine talked about in MM2000 before the wonderful mag went to the EAStside.
Also, like many have said you can use Vitamin E oil. Stretching or warming up is nonsense that has nothing to do with the skin's inabliity to grow as fast as the muscles beneath it. GH is another way although, more expensive, to help to b/c it will help the skin (epidermal) layer adapt to the skin's high need to increase surface area due to expansion of muscle tissue beneath it.
Best of luck but just be happy you have stretch marks to complain about.