Birth control

So I came off the pill on 27th September to TTC, I then had a withdrawal bleed.

My predicted ovulation date was 14th October. I have used OPKS (from 11th October) and all negative.

I know natural periods can take a while to come back so when is the earliest I can test for pregnancy?

I have been told to wait till the day after period is due but not sure how I know when that is 😫