@Nightingale - I'm sorry you're feeling so bad, but this is only going to be temporary.
Things are going to get better.
It's only 9 days since you had major surgery that caused a lot of trauma. Of course you can't do everything you want to at this stage. Your knee and your body need time to heal and recover from the surgery.
It's not the sort of operation you can bounce back from in just a couple of weeks. In fact, complete recovery from a knee replacement takes as long as a full year, although you'll be able to do most things by about 3 months.
If you're in pain, of course you're going to feel grumpy - who wouldn't? Be patient. Take care of yourself and your knee by getting plenty of rest, while icing and elevating your leg. Take your pain medications on a regular schedule.
Take short walks around the house. That's all the exercise you need right now. More will come later.
Most people lose their appetite for a while after this surgery. It will come back gradually.
Did you read all the articles that Jaycey left for you in Post #2 ? Take particular notice of these:
Activity progression for TKRs
rest
elevate
ice
take your pain meds by prescription schedule (not when pain starts!)
don't overwork