Hi, and thanks for your medical question on eHealth forum!
Burning in urine can be due to urinary tract infection. The other possibility is that you have a stone in the urinary system, which though is asymptomatic is acting as the source of infection. It can also be due to a STD if you also get UTI after sex. Non specific bacterial infection, or fungal infection can also cause recurrent UTI.
What you need is a urine culture and sensitivity test done. This will tell you what organism is causing the infection and what antibiotic will kill it permanently. Please do not take any antibiotic without this test because if the organism is not sensitive to the antibiotic, it will only sit quietly for some time and then flare up again.
A simple urine test should also be done to look for RBC, leucocyte esterase enzyme, WBC etc. Please consult your PCP for this. Hope this helps. Take care!