Trying to cycle track my periods whilst BF?

Okay I’m so confused! I’m breastfeeding my son still but I’m trying to track my cycle so I know when I’m ovulating and when I’m due my period as I’m really irregular! Every time I test my ovulation, this is what I get (please see image). I’m testing every two days, but it’s always this dead faint line (indicating negative). My periods are so irregular and keep catching me off guard! I’m SUPER heavy and really struggling with them! My cycles are like 56 days long, then 39 days the next! Anyone else going through this? Any advice?