Light spotting- pregnancy - ovulation.

Hi Doctors, I am 25y old who had unprotected intercourse in 27th March and got my periods on 28th March which lasted for 4 days, didn't took any ipill or any birth control pills. Was admitted in hospital on 31st March and 1nd April because of two stones found in kidney and in urinary pipe which were removed by flush therapy and with lots of antibiotics and injections. Now, on 22nd April at night, i experienced light brown spotting, and then on 23rd, little flow of pinkish type blood but it is so slow that pads are not being used. And today on 24th April, there is blood in vagina but it is not having any flow similar to menstrual flow.its light, it's inside and there is no need of pad. I am worried what is the cause of it? Is it medications or the unprotected intercourse a month ago, or any other areas.