You just had major surgery and they removed the majority of your stomach. You are not eating solid food, probably aren't yet getting your full amount of suggested protein/water and are very low on calories even if you are managing to meet your goals. Of Course you're tired and weak and having some pain.
It is hard and can be scary, but please give yourself some time to heal. It can take several weeks to even begin to feel semi normal, which is standard after any major surgery. Rest up, drink plenty of fluids and try to get your protein in. You'll feel better soon.