NEVER A DULL MOMENT

I'M 8WKS POST OP ON WED. I'm down 41 lbs, and feeling great until Fri. My knees hurt!!! Out of the blue, they just ache. I have not done anything to injure them or cause strain. If it's not one thing, it's another with me. Over the weekend, I took it easy, but it did'nt help. What kind of flare up is this,? they are not red or swollen. I'm so bummed,and discouraged. I can't work out or walk, I am bored out of my mind. Any suggestions