TTC Newbie

I recently got the app to help me conceive or as I'd been reading, a BFP. I have an irregular period and I can sometimes track my period and sometimes I can't. When I do get AF my period lasts 7 days and comes 24-28 days after my last AF. Well I got my nexplanon taken out Sept. 9th and when I set this app up it tracked my fertile window from Sept 4 to Sept 10. Is it possible to get pregnant or not? I haven't gotten my AF and it was supposed to start yesterday. Could it be the because of my nexplanon being taken out?