OPK and late ovulation

So this is my first month of TTC #2 and I have been using OPK to see when I ovulate. I'm now on CD 18 and am yet to see a positive test ☹
I have only had 1 period since being pregnant and only just finished breastfeeding so my cycle would come back, so I'm not to sure what my cycle is like post baby. Pre baby I was very regular, 28 day cycle
My question is: 
What's the latest anyone has ovulated that they know?
Has anyone tracked their ovulation and not got a positive test but still got their period?
How fast did your cycle regulate after weaning?
I know this is only my first cycle back but I'm stressing my self out thinking there is something wrong with me when this could be quite normal?