Man, if you're causing bleeding, something must have hurt first. There should be no pain with this process. I suspect you might have a problem with yeast. Skin does not ordinarily tear unless you are really brutal with it.
Get a topical cream meant to treat yeast. One common brand is Lotrimin. Apply it to the foreskin, especially at the tip and inside as much as you can. If you have yeast, this should get rid of it and allow you to stretch the skin without fissuring.
Instead of trying to stretch by pulling back, do this:
Do two to three 10-15 sessions per day.