You need to find a doctor that will listen and take your symptoms seriously.
There are too many things going on that need medical attention. With the vomiting, diarrhea and the nightly sweating and feeling cold, you may have a kidney infection.
Make an appointment to see a doctor and take a morning mid stream urine sample for testing. You can urinate into a clean clear jar and look at the urine. If it dark (which can be from dehydration, but also blood); cloudy; smells strongly - this could indicate that you do have a infection in the urinary tract. Having kidney stones can also give you these symptoms.
As you have put on weight and feel cold, this may be a thyroid problem.
Because you did have cancer, it is more important to get checked out to ensure that this has not returned.
Make an urgent appointment to get seen my a doctor. Consider going to the ER if your symptoms do not improve.
Don't allow the business health care facility not to listen to you. You need medical attention urgently. Make an appointment with a different doctor.
Hope you get the medical attention that you desperately need.
In the meantime drink lots of fluids, but take small swigs often. With the night sweats and the persistent vomiting and diarrhea, it is highly likely you are getting dehydrated. Drink clear soups and buy the solution that you mix (from the pharmacy) that will replace your electrolytes.
If you experience that pain, it may be a good idea to get someone to take you to the ER.
Let me know how you get on.