Thanks for the query.
Ideally you should do a urine culture prior to starting antibiotics.
Also urine infection is rare in a young male. Thus if you have symptom again you need to see a physician who will do further tests to determine if you have some other medical issues leading to UTI.
often produces diarrhoea
as a side effect
So see your GP who can prescribe a different antibiotic.
Hope this helps.