@emmafontaine Some thoughts...
1. Work out before work, then you don't have to take any workout stuff with you.
2. If your gym is close to work, leave your home dressed for the gym, go to the gym, do your workout, quick shower there if there are showers, and change into work clothes.
3. If you work out during the day after a couple hours at work, just bring an extra set of underwear instead of an entirely new outfit to change into after your workout. Just change back into the work clothes you started with that day after your workout.
4. If your gym doesn't have a shower, moist towelettes and dry shampoo can keep you feeling fresh until you get home later to take a shower.
5. Commit to fitting everything you need for the day in one bag. It will force you to be efficient with space.
6. If you have a fridge at work, consider taking food for the week on Mondays so you don't have to carry a lunch with you every day.
Best of luck!!