UTI or Kidney infection?

Hello, i am 46F, 75kg/ 166 cm, diabetic t.2, non smoker taking Glyclazide and levotheroxyne, 5 years ago i had Oxalate sensitivity. in last few weeks about time i developed candida on vagina etc and from Dr got hydrocortisol to apply, i noticed weak muscles, and shortness of breath whener i do some activity like walking for longer time, plus diarrhea couple times a day, esp after coffee. Once about 2 weeks ago stabbing pain on right side of upper back for few hours after eating salty high oxalate food. I also noticed some sort of inflammation when i touched my lower backs, like stiffed muscles or something.

Then typical Uti symptoms came such as pressure on lower stomach, after pee, slight chills/ hot flashes, like one minute cold then hot but not extreme. Now last few days it gets worse with very bad fatique, nonstop nausea, feeling like vomiting but didnt, muscles very weak, mostly legs, no strength to do anything, walking slowly, unable to concentrate and sleeping a lot.

I called Dr she confirmed its Uti, but said my urine sample does not show anything. I started Nitrofurantion.

This morning i felt much better, most symptoms gone, however when i stood up in kitchen after 10 mins my very low back ( just above arse was aching a bit and the area feels tense, but it could be new bad chair i sat in 2 days ago…

I am not sure with feeling so low can be just Uti or does it now spreads to kidneys. Is it possible even if urine test does not show anything, no temperature ( just felt a bit hot yesterday when touching forearm and colder than usual), no vomiting no blood in urine? I think the hydrocortisol i overused for month started these issues. I dont know. Is there way to tell by touching the lower back area?