Faint line but long cycle


My cycle has been so irregular and long that I haven't been able to figure out when I am ovulating. According to this app AF is a week and a half late. But I was doing the averages of all of my other cycles and if I use those numbers AF should be here tomorrow. I took a test from the same box this was in last week and it was a BFN but now I have this. Can I trust it?