Late period or postpartum irregularity?!


So I had my baby boy 4.5 months ago and my period returned around six weeks after birth. Since then it has been very regular, every 28 days (as it was before) for 3 months- however this month I am 5 days late. Negative test this afternoon but haven’t done a morning test yet- pregnancy or just irregular periods after birth (although they had been very regular?)

Thanks in advance, one worried mummy 😫