Pregnant again using pullout method one time after giving birth?

I gave birth to my 4th child 15 weeks ago.

I am breastfeeding and with no contraceptives.

I had ovulation spotting and had unprotected sex using pullout method within the 24 hours of the spotting.

A couple of days after, I had a strange rumbling sound coming from my uterus area.

My nipples suddenly became sore when my baby latches for feeding and this has never happened before.

I am now 6DPO and I am having faint cramps on and off and my cervix feels mushy and somewhat tighter.

I strictly breastfed all of my children. And when my firstborn was 3 months old, I had sex only one time using the pullout method ended up pregnant with my 2nd child before I got my first period.

When my 2nd child was 3 months, I ended up pregnant the exact same way.

There is a 4 year age difference between my 3rd and 4th child...

but could history be repeating itself and I am pregnant again based off 1 encounter with unprotected sex using the pullout method based off my symptoms and previous pregnancy history?

Btw, all my children are fathered by the same man.