6 days late, negative tests.

I am six days late and I've taken two pregnancy tests and both negative. My SO and I have talked about it and don't understand. I just got off of my BC (mirena) about 2 months ago and had a period shortly after getting it removed. My SO and I have an appointment in a week (if my period hasn't came yet) to figure out if something messed up when removing my mirena. Should I be worried or what should I do?