I know exactly what you're going threw, I had my tonsils taken out about 3 years ago, not fun at all. I don't know if you've talked to any adults who have had there tonsils taken out, but it's not as easy as it is for kids. I was in bed for about a week and a half, fighting with myself to keep water and meds in me. Even though I had liquid pain medicine, it still hurt so bad to take it, but I knew that if I didn't it would get even worse.
But here is what advise I would have wanted someone to give to me.
Find something, anything that you can eat, popsicles are amazing.
Drink as much water as you can, if it dries up it could cause serious problems.
Take your pain meds as often as you can, easier to stop pain before it gets bad.
Don't eat or drink anything that is acidic, I made that mistake with tomato soup, milk isn't the best idea either.
Soon as you can, slowly and carefully walk around the house or outside, but don't push it.
You will lose weight just because you wont be able to eat anything. But after about 2 weeks, you will feel amazing, and you will be able to jump right back into everything you've been doing. Don't let it get you down.
I hope this helps and good luck with the surgery!
~Angela