Pregancy after pill

Hi,

I came off my pill in early October. The last day I took the pill was 11th October. I had read that

as I had stopped mid-pack I may have a withdrawal bleed.

I started bleeding on the 18th and stopped on the 22nd. It was what I expected of a period, it was heavy for a few of those days, i had uncomfortable cramping and pms!

I am not sure if i had a period or withdrawal bleed!

The calendar on this app tells me im in my fertile window already! I did have a sharp shooting pain in my right side, low down on saturday afternoon for a few seconds.

Could this be possible?