Not feeling connected to your child, almost a disbelief your child is growing up? A name for this? Pls no rude answers.?

I noticed in June of 2019 a month after my son turned 3, one year after his dad and I legally separated. Idk what happened, it was almost like when he started preschool/summer camp that June, I was in disbelief that he was in school and having actual conversations w/ other ppl. I noticed earlier in 2019, he began speaking more and more when he was still 2 and I was so happy he was developing like a normal child. Seems like something w/me being a single parent and not married anymore a yr later and him growing up without his father and I to both witness threw me off cuz idk how else to put it. I did have bad postpartum after he was born that lasted 3 1/2 months, but that has long been gone. I'm over protective of him and do anything a mom does for her little 4 year old but even now since June 2019, I feel like he grew up too fast or he's not really my child. It's hard to explain. Again, I still think it has something to do with his father and I now being divorced. Is any of this regular what I'm feeling. I try to ignore it, it comes and goes.