Originally Posted by
pannb
I have a carbon fiber road bike and 700C-23 tires.
There's your problem right there. You need a much heavier bike. Fortunately for you I live nearby and am willing to trade with you. Seriously, most would consider a non carbon bike with a little wider tire to be better suited for commuting. Also, try riding just every other day at first. Your body will build up to it quickly.
Research the side walk riding thing. It can be more dangerous than riding in the street.