Is there any way you can keep some of this stuff at work? I do wear a backpack but it's a minuscule one holding only wallet, cellphone and keys, and I can barely feel it's there, sitting between my shoulderblades. I stow several changes of clothing at work, shop on the way and put lunch in the fridge there etc. I don't like riding with a rack and panniers because I don't like the way my bike feels with it on, but I can get away with carrying very very little.
If you have to ride with stuff I'd go for the pannier solution, and just tweak the bike enough to make sure you can handle keeping an eye on commuter traffic without getting back pain.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett