Thank you for the query.
Such recurring UTIs needs to be diagnosed as can lead to kidneys severe inflammation and failure.
From your symptoms it sounds like you may have kidney stones. It is very common that such stones can not be visualized in the CT or ultrasound and the only proof of its presence is recurring back pain radiating to the lower abdomen and groin.
Other reasons like narrows in the ureter can result with chronic utis due to impeded urine flow.
Increased blood sugar level (diabetes) makes us prone to utis as well.
are very common findings and most of them does not need any action except observation.
Kidney stones are thought to be caused by diet, but as there is few types of stones and every type needs different diet, it is hard to advise which diet you should have. You definitely should drink a lot of mineral water (like 2-3 l a day). Increase physical activity. You may try to decrease sodium intake, animal proteins intake, avoid foods high in oxalate, such as spinach, rhubarb, nuts, and wheat bran.
should perform cystoscopy
and urinary tract
check with contrast.
Hope you will find it helpful.