Zithromax Z-Pak and lubricant

I am 61 years old and weigh 79 Kgs. i am 175 cms tall. I was given Azotik - 500 one a day for three days. It contains Azithromycin Dihydrate 500 mg. On the 2nd day of my taking this I noticed drops of blood soon after masturbation which i first thought to be due to a colour in the oil that I used as lubricant. On the 3rd day of medication I could see more of blood which again i thought to be due to the oil. But I also suspected that it may be blood from urine. So i watched urine for three days and found no color. So as a cross check on the 6th day I masturbated again and to my dismay I saw blood was spurting out along with semen. I am deeply worried. please advice me on this.