I have a urinary tract infection with no fever or backache. do i need an antibiotic?

Check culture report: If you have a urine culture report which confirms that you have a large number of microbes (more than 100,000 bacterial colonies /ml in your urine) you would be considered to have an "asymptomatic bacteriuria".The choice of antibiotics would then depend on your medical history/your clinical evaluation,on the type of bacterias that are identified and on their sensitivity to particular antibiotics.