What to do? Other comments or ideas?

I am ebf had my first postpartum period at 3 months pp I am now almost at 8months pp I have not received my period for December and still currently waiting I am 19 days late for Decembers period I have taken multiple hpt and all negative and including a qualitative blood test at 7 days late which was negative. When or should I even contact my OB or just start a new cycle for January? Or should I wait out this month expecting that it will come ? I did a poll maybe a week or two ago asking if it was common to miss or skip a period but at what point should I be concerned? Thanks!