Period a day late?

J
I had the Mirena removed on Dec 18th. While on the Mirena, my 30 day cycle has been consistent like clockwork. Now that it's been removed, can I expect my period be late as my body may be regulating itself? Or is it possible that I may be pregnant? I took a HPT this morning and it showed a BFN. Should I test again a week later if AF still doesn't make an appearance?