Post coital bleeding 15 months after colposcopy

Hi everyone. I experienced post coital bleeding on march 2018. I had my first smear test on december 2016 in which the doctor found precancerous cells on the cervix and they were removed. So i went for my first smear test since then today but I dont understand why this is happening as i was told that i would be fine for the next three years and i thought cancerous cells took 10-15 years to develop. Has anyone else experienced this?

Smear test dec 2016 

Precancerous cells removed dec 2016

Smear test april 2018