I would test. I am also in my 40s. I had my youngest 19 months ago. I breastfed her for a year and my periods returned after I finished breastfeeding. I had one very late period and wasn’t pregnant. My hormones are all over the place. I am having some other perimenopause symptoms. I was regular for about 4 months and then had a late one.
Mine are irregular due to stress. I turn 40 this year
Sometimes I ovulate late when I'm stressed. Could be perimenopause too.