When is my Af due?

[Gem173]

Hi guys, sorry for such a stupid title lol
But I'm not sure when my AF is due. I have recently come off the pill (21st Sep 17) and am aware I might not even get a period for the first few months but still want to know the days I should just keep an eye on. So I had a withdrawal bleed on 23 Sep to 26 Sep and had a pos opk on the 12th oct. now I'm not sure what the length of my cycle is so if it is 28 days, my af should be due this weekend, but if that's right it means I could have poss ovulated quite late. Two weeks from ovulation, means af could also be due around 25th oct (that's for a 33 day cycle which I tested on ovia and gave me the right fertile days and day of ovulation). I'm so confused.
If anyone can help as to suggest a day my af will come, I'd be grateful!

Generally you always start af about the same number of days after you ovulate. For most it’s about 12-16 days between the two. Forget about 28 day cycle, as the time between when af starts and ov happens can vary, especially when coming off the pill.

@Physicskate thankyou I am worried I will have A short lutenal phase after coming off the pill. Seeing as the phase before ovulation was quite long, it might be short, but if it's 12-16 days average then I might be okay :)