Pregnancy after Mirena...

Hello all,  
 So I'm quite new to this so please bear with me if I mess something up. Ok soooo I used Mirena for about a year and a half after my son was born. Previous to it I had a normal period every 28-30 days with no issues. While on Mirena I would only get some spotting every once in a while. I had my Mirena taken out on October 31. I had my first actual period on November 28 and it lasted like 3-4 days. According to the <a href="">Glow app</a> I should have started my next period on Dec 26th and when it didn't come it said Dec 29. I adjusted it again and it now says Jan 1. Pregnancy test (dollar store brand ha!) this morning said negative. I'm not really sure what's going on. Anyone have this issue after stopping the Mirena? Or any advice from knowing someone that did? Any advice would be helpful!  Thanks in advance