Late period

So according to this app I’m two days late on my period. But before I got this I was on birth control for a very long time.

I was on pills from the very beginning and then I switched to the Nexplanon implant and was on that for like 2 years and after having a lot of issues on that I took it out and got put on the shot but only did the shot once. I’ve been off birth control since September and have only had one normal period back in December so I’m wondering how accurate my app could be?