Leena,
Welcome to OCF. I'm sorry you've had to go through this, but as some of the others have said, you're at a stage where you should start to see some improvement in the near future.
My weight went from around 130 to 112, mostly during the latter weeks of radiation. My doctors had warned me from the start to be diligent about keeping my weight up as much as possible, so I kept trying to force soft food down even when it was painful and tasted terrible. (I never had a tube, so I can't comment on that alternative.) I had regular visits with the nutritionist at the hospital, who kept close tabs on my weight and tried to adapt my diet to deal with whatever eating problems I was having.
I hope things start to get better for you soon.
Cathy