Help me work this out

[Kona84]

Average 29day cycle can sometimes be 30days.
1st day of last period 19th Sept. unprotected sex on the 28th sept cycle day 10.
Today is the cycle day 20 and I am feeling twinging on my lower left side.
If I count 14 days after 1st day of period for ovulation I land on the 2nd October which means 4 days after sex. Could the twinges be implantation?

A fertilised egg usually implants between 7 and 12dpo so it's possible.

The issue I see is that you don't necessarily ovulate 14 days after the start of your period.

Yeah I was just working on averages.
I haven’t tested my ovulation yet so not sure when I do ovulate.
At the moment we are not preventing but not fully trying either. If it happens it happens, I’ve just been feeling really weird this week.