I Had A Partial Left Knee Replacement, It Is Now

I had a partial left knee replacement, it is now 6 weeks and i feel very tired still and stiff. I wake up several time a night and toss and turn a lot trying to find a good position for my knee. Also i can only walk 2 block slowly before i get tired, i will be looking at doing the same surgery on the right knee in the next 6 months. I have OA. I am 50 but work on film set standing and lifting things up and down stairs for 80 hours a week for months for the last 25 years, so i am used to hard work and i have a lot of stamina. I hear it's normal to be tired. My short term disability claim ajuster keep calling and asking how I feel and wants to know when i can get back to work, not sure what to tell him and when i can do my work or if i can do my work again... Let me know what you think as far as work goes. Thanks you very much