Your poor knees!
They've been through major surgery that's caused a lot of trauma. They need time and gentle treatment, so they can heal.
Whether you like it or not, that healing takes a long time - as long as a full year for all your tissues to heal completely.
At this stage in your recovery, consistently doing too much will prolong your recovery and cause you more pain.
Slow down, shop online, and find a hobby you can pursue while you're resting.
You may find this aspect of recovery hard, but dig deep for as much patience as you can muster, and know that in doing that you are giving your knees the best opportunity to recover.
If you persist in doing too much too soon, it is possible that you could set up a scenario where your knees become chronically irritated and inflamed.