Again another post from 2009-no reason to bring up and post on old threads.
Thanks
You probably just have sensitive skin down there. It is a common problem actually. Start using a penis health creme. These cremes help with all sorts of issues down there (redness, itching, flaking, rashes etc). It's nice that you can rule out an STD, so try using a creme daily and I bet you see positive results. Good luck.
This could be anything but doesn't sound like an std... I think should work closely with your doctor.... one doctor that you trust, it may take a few visits but this is the best thing you can do at this point.