Tell me why!?

Ok so I have been a regular 28d cycle person since I got my period one day late at most! I finally got my period in October after having my son (8m pp) and the Nov Dec ones where right track like they’ve always have been. We tried for a baby on my fertile week (23rd on) my period was due the 9th of this month I am now 7 days late (today 8)!! I’ve been testing and everything is NEGATIVE not even a hint of anything. NO SYMPTOMS either.

Nothing has changed with my diet or physical activity. Only stress in not getting my period lol.

Now my question. Anyone ever keep testing negative and be pregnant?

Anyone miss a period and have it be something else besides pregnancy (and needing a Dr)?

At what point do you call a Dr?

Thanks