Go to the hospital ER urgently. You may be dehydrated with having persistent vomiting.
You need a thorough examination, blood tests for kidney and liver function and a urine specimen test and an ultrasound in the area of your bladder and kidneys to find out what is going on. The hospital may decide to do other types of imaging.
It is possible that you have a severe kidney infection or the possibility of kidney stones. You do not say where the itching is, so it is difficult to say if this is connected to the other symptoms that you have or a separate issue. You do need urgent attention with regard to your other symptoms.
In the meantime, make sure you keep drinking plenty of water. At least 2 litres in a day (not all in one go though).
As you feel nausea and keep vomiting, take little swigs of water often rather than drinking a whole cupful in one go.
Get a clean glass jar so that you can urinate into this and observe your urine. If your urine smells strongly, is very dark (sign of dehydration or blood), is cloudy, then it is highly likely that you have an infection in the urinary tract. You may find sediment may settle or you may see little grains that settle to the bottom, this could be kidney stones breaking up. Kidney stones can be any size and from as small as a grain of sand.
Let me know how you get on.
Wishing you a speedy recovery.