Figuring out my cycle and ovulation days

After I had my daughter I decided to start depo and kept it for two years and now I have been off it one year and 2 months...my cycle used to be on point and regular however now they are far from it...I've been having the most stressful time re figuring my phases and ovulation days. It's become a little easier and I've been tracking them for about 5 months now but the variations are so different... Any tips from ladies ttc would be awesome....!