Doubt case of pregnancy. Chance.

Hello, Doctor, Used a tablets for postponement of periods in the month of Oct and got on 7th of Oct instead of 4th. As I am not well I used medications for 2 weeks for fever nad cold and weakness.  me and my  husband had an unprotected sex back to back. I got a symptoms of bleeding exactly on 7th of Nov but I am not bleeding. I am just spotting and I can't see even that untill  I wipe or check with my fingure.I went on home pregnency test yesterday and it was negative. my spotting Colour is brown rather than red and it's not continuous . I didn't face this kind o issue before. As I was admited in the hospital year ago due to dengue and used medicines I couldn't see this happened.my period was on date. Can you help me out with the answer that if not a pregnency what could be the possible chance. Thank you in advance Hoping a immediate reply