What would be some good things to take to rebuild damage muscles?

Amino acids are the building blocks of protein. Protein is what is needed for muscles. BCAA or brain chain amino acids are especially good for helping with muscle atrophy.

I take BCAA because of problems I have had with fatigue and muscle weakness.

I am not sure what you mean by damaged muscles.

Over the last 5 months I have undergone 4 major surgeries due to complications on my right knee and experienced significant muscle and tissue damage. While in the hospital after my third operation I was put on a trail program using a new product called JUVEN. Juven is a specialized high concentration of HMB, L-Arginine and L-Glutamine amino acids and calcium in a powder form that you mixed with water or Gatorade and take twice a day. (It’s not cheap!) I am still using the product now 8 weeks post op from my last surgery and I have seen great improvements in my muscle strengthening and experiencing little to no deep tissue pain. I was totally off pain meds within 5 days from surgery. I have also seen marked improvements in my stamina.
Does it really work? All I can tell is, I have 1 more surgery scheduled in 3 days and I plan on continuing to use Juven as part of my therapy. The cheapest place I found this product is at Walgreens @ $17.99 for 8 packs on special order and takes about two days to get the product for you.

protein is essential for muscle growth, especially the amino acid leucine which is what tells the body to build muscle. At least 20-30 grams of protein per meal. Also, take high doses of omega 3 fatty acids. They are proven to help maintain muscle mass and reduce inflammation that leads to tissue damage. 3-5 grams of EPA & DHA.

to add to what others have said:
1. over the counter protein powders. choose one without sugar or fructose.
2. carnitine supplement
3. your diet is key, I would cut out the carbs and sugar and focus vegetables and protein intake.

with the help of your doc, you can get tested and supplement the following if low on lab results:
1. testosterone
2. dhea
3. growth hormone