T.W.
It could be one of 4 different things going on.
1 - I nursed all three of my kids and with the 1st two, it took 6 months or more for me to get a regular period after I weaned them. Basically it took 21 months to screw up my hormonal system with pregnancy and nursing that your body needs a bit of time to get back on track. So it could just be that you quit nursing and your body is readjusting.
2 - IUDs are also hormonal and it is not unusual for it to take a bit of time for your body to get back on track after having them removed so irregular bleeding is expected.
3 - You will get your period today because you just typed this request. : )
4 - You are pregnant and it is not showing up on the test yet. My third baby did not follow a single rule that the other two did. My symptoms were different, I carried different, I felt different, and it took three tests to show I was pregnant.
So I say wait it out a bit, the answer will come.
Good luck!