Cycle lengths question

Hey y'all! I had my implanon removed in October. Here is the length of my cycles since then, followed by a question. 
Sept-oct (came off AF the week I had it removed) 31 days 
Oct-nov 30 days 
Nov-dec 27 days 
I'm not sure what my cycle length was before I had implanon but tomorrow is CD27 for me and I am having no symptoms for AF. So my question is, has anyone had their cycles sort of even out and stay at one length (give or take) after coming off BC?? I am wanting to test tomorrow but this app as well as ovia have me down for a 30 day cycle putting AF due Wednesday 12/31. I'm not sure what to trust as far as my last cycle length compared to what the apps are saying. I am assuming they use an average length to determine the due date for AF. Seeing how my cycles have gone down in length over the last 3 months I want to hope it stays at 27 days. 
Sorry for the novel ? 
Thanks in advance!