If you aren't able to practice those things that I suggested without it bothering you at the slightest touch, maybe you should see your doc. He may have other suggestions for you or better techniques.
I am not sexually active, and its easy to pull back when my penis is not retracted but the only problem then is that it is very sensetive even if it is touched only by the slightest.
May I ask, are you sexually active? I ask because, the skin usually gets forced back during intercourse. If you aren't, then maybe you should try training the skin to retract by gently moving the skin down each day. Maybe when you're in the shower and soaped up, you can try.
Or does it usually retract except when erected?