Thankyou for writing to health care magic!
I have read your question in detail and see that you have a constant stomach ache, initial vomiting; and cannot eat much now. You feel very weak due to all this.
From my experience I can tell you that one can experience weight loss
in two days of not eating adequately. Moreover, you had been sick for more than two days as you mentioned that you had stomach aches from past few days before vomiting, which also reduces intake of food.
I think that you are either having severe gastritis
or some abdominal infection. This can be treated successfully with antibiotics, antiemetic and antacids. As you are feeling too weak to stand, I'd suggest that you should make a visit to some doctor .
For the time, take adequate water, go for soft foods, or some fruit, if you feel like. Avoid anything spicy, or oily for some time. Start with few sips of water or few bites of food, once you are able to digest it you can gradually increase the amount you eat. This will help you regain strength.
Hope this answer helps you getting better.
Dr. Manisha Gopal