On days when you are going to work by car, drop off a towel, shower items, a pair of shoes, and maybe a few sets of clothes. Then you can carry less when you ride. Hopefully you have an almost empty desk drawer to store such things in. If you need to lock your bike outside, leave the lock attached to the bike rack (or whatever you lock to) overnight and don't carry it back and forth. Or keep the bike in your office during the day if you can.