Welcome Allisyn and Romeo. This is the best place you never wanted to be, for information and support while you learn about effective diabetic treatment for Romeo.
Unfortunately, many vets are just not as educated in feline diabetes as we would like. But there are members here who have been managing feline diabetes for years, and have the knowledge and experience you can draw on.
There are three main components of effective treatment: diet, insulin therapy and blood sugar testing at home. If Romeo isn't eating that needs to be addressed right away, especially if you are already injecting insulin.
Please tell us what antibiotic/treatment vet has prescribed for the UTI, if that has been determined. Has vet taken a urine specimen or culture to determine if a UTI is present?
Also, the 4 U of Vetsulin as a starting dose is
most likely too high. It's better to start low and work upward as needed. Please reconsider that dose, post and let us help you work on these issues. But, Romeo not eating is the greatest concern right now, and if you are injecting that big dose of insulin, you might be setting the stage for DKA (Diabetic Ketoacidosis) which is a very serious condition and can be life threatening.
Testing Romeo's urine for ketones (with Ketostix that you can get at any pharmacy) is a good indicator if DKA is in the picture, and here is some information about that condition, just so you know.
http://www.felinediabetes.com/FDMB/...oacidosis-dka-and-blood-ketone-meters.135952/