WHAT CAUSES BLOOD IN SEMEN? IT STARTED IN 9/2017 AND

WHAT CAUSES BLOOD IN SEMEN? IT STARTED IN 9/2017 AND IN ABOUT MAY OF 2018 I TOOK 3 MEDICINES FOR H PYLORI AFTER FINISH THAT DOSE OF MEDICINES IT SEEM LIKE MY SEMEN STOPPED BEING BLOODY UNTIL AUGUST. I HAVE NO OTHER SYMPTOMS OTHER THAN BLOOD IN MY SEMEN. MY UROLOGIST DIDN'T THINK ANYTHING WAS WRONG. MY OTHER DOCTOR DID A URINE SAMPLE AND DIDN'T FIND ANY BLOOD. THANKS