Late period

I’m freaking out cause I have a 3 month old and a 1 year old😂

i’ve been on birth control again officially a month and haven’t missed a pill, doing pull out method besides once but the period app said my chances of pregnancy were low. last period was nov 14 it’s now 4 days late according to this app according to another it’s 9 days late (the cycle lengths are different cause I honestly don’t know mine) I took a test tonight and it’s negative, I googled and it says flu can cause a period to not come and I just tested positive 4 days ago so what are the chances? this would be my second period after having my baby I just don’t understand why it’s late😵‍💫😂