What’s happening

a

I had my baby is September.

In November I had my period on the 9th ended on the 13th.

Than I had my period again on the 21st of November to the 25th.

I only pump breast milk because my child won’t latch to me.

I haven’t got a period since.

I’m no 30 days without a period.

I took a digital test on December 27th and it said negative …

Should I be retesting or is this just normal ?