My 12 year has had a very strong fishy smell in her urine for a long time it's worse on her period too doctors in our town can't solve some advise ?

Infection testing: The doctors should do a urinalysis and possibly a urine culture. They should also do a vaginal swab and bacterial vaginosis which is a common cause of vaginal odor around the time of menses. Other infections should be tested as well. If all of those are normal then the pediatrician can evaluate for some of the rare causes of malodorous urine which can signal metabolic disorders.