Good work! my fat ass is about 250# (well, that's the ass plus everything else) and I bike commute every day. You should pop over to the Clydesdale&Athena forum also for support and advice. You can do it, especially if you work up to it, and also consider options like partway using public transit, or drive partway with your bike, then ride the rest. Gradually increase the biking distance and #biking days, and before you know it you'll be a full time bike commuter!