Is this normal?

My app says I ovulate tmr which is CD 20, I have been testing since CD 12. I gave birth to my son in February and he passed away 30 mins after birth. I’ve only had 3 periods and they were between 30-40 days so I kept missing the ovulation date. The apps weren’t correct and I hardly had any CM to figure it out myself. I purchased the ovulation kit on amazon that people suggested. This is my first time using it. All these tests seem to be negative, I also take my bbt every morning and in my Fertility friend app today after I took my temp it changed and said I ovulated on Monday CD17. Does anyone notice anything? Any help would be great!