Good Morning and welcome. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
It is hard to know what may be causing your cat to not feel well but in many cases, if your cat is an outside cat, this is due to an abscess brewing under the skin somewhere on the body from a cat fight. Check your cat all over for any small lesion or scab that may indicate a problem. If you find this, apply hot compresses to this area to draw the infection to the outside.
If your cat is older, vomiting is the first sign of Kidney Failure and this will require your vet to examine your cat.
Please let me know if I have missed anything...I am happy to help....
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please Reply so I can clarify for you
Sincerely, Dr. Loretta