I handled treatment pretty well and wasn't gaining weight at the 3 month mark either. If you were to make a pie chart of how your calories are being used almost the entire pie would be "repair". Weight is gained (in simple terms) by taking in more calories than you use. Even 3 months out that is a tough equation. My weight gain started right after I returned to the gym. My first visit back was horrible as I had lost a great deal of muscle mass and had no energy at all. I might not have ever gone back but my wife pretty much made me go 3 times that week. I gained 4 pounds. It's almost as if my body needed some sort of signal that things were returning somewhat to normal. My pie chart was still mostly "repair" with an ever increasing slice called "building muscle".

The best advice I can give you is to become active. Please do not compare active now to what active was before treatment. Just do what you can, especially when you don't feel like it. It will start positive momentum that can carry you through. I am actually a better runner now than before treatment because of the discipline I was forced to learn during my fight.

Godspeed!