Oh, no! You are way too early in your recovery to be doing all you are doing, especially driving. Would you have been able to slam on the brake if you had needed to? I doubt it. Were you able to bend your knee enough to comfortably get in and out of the car and keep your foot on the accelerator? Bless your heart no wonder you are in pain and increased your swelling.
Please stop treating your knee like it's 2-3 months old instead of only 3 weeks old.
Please stop treating your knee like it's 2-3 months old instead of only 3 weeks old.