Don't be surprised if the swelling lasts for a couple of months or more, not just weeks. You are doing fantastic for only one week out, but be careful to not overdo it. Your knee is very traumatized after this surgery and will get angry very easily.Knee is still very swollen, but pt said that was too be expected for at least a couple more weeks.
Being exhausted after a short time up is also normal. Your body is concentrating on healing that knee and that takes a lot of extra energy.