Ttc #2 cycle #2

So it seems my current cycle is almost the same when I conceived my first. With her cycle start sept 7th 2017 . And we conceived either sept 19 Or 20. Her due date and birthday was june 14th 2018.

Now my current cycle started sept 6th... And i dont know when I will ovulate... I dont use anything other than cervical checks.

Am I being weird if I don't want to ttc this month for fear they will have the exact same birthdays?