Really worried please help

So my ex and I just had our 3rd child on feb 28th and I bled for exactly 5 weeks. We made the mistake of hooking back up twice after I was done bleeding. On the 4th we used protection and on the 7th we did too but it ended up not working and it was all inside of me. I don’t think this chart is correct when it comes to me ovulating after I had a baby. I’m so scared that I could be. Does anybody have any info on ovulation after having a baby? I did just take a ovulation test today (I know a week later...my kids father left me for another girl and left me home with our kids without a vehicle so I couldn’t get one sooner. 🙄) so today it came up negative for ovulation. Is there anyway I can find out if I already ovulated or do I just have to wait and take a pregnancy test?