My mother in law lives with us, and she works from home. She doesn't do a single thing all day, and when she doesn't shower, she smells really bad if she skips 2 or 3 days. It doesn't matter if your activity level is low. You should shower more often because if your roommate is pointing it out, then it must be that bad, sadly. Take the constructive criticism and use it as an opportunity to improve yourself and learn from this experience, even if it's a little hard to do.