Someone please help me understand! Really need answers

I’ve posted before and got no answers and I really need some opinions, my doctor isn’t much help at all. I’ve had two chemical pregnancies and two miscarriages with no healthy baby, my doctor doesn’t seem to be concerned about the chemical pregnancies and says they happen very often. She says I should only worry if I have 3 or more actual miscarriages and to keep trying for now, I have absolutely no problem getting pregnant but keeping it seems to be the issue. I’ve tested for pcos and I don’t have it, what else could it be? Or is this really normal? Has anyone else gone through something similar and had a healthy baby? What could keep causing me to loose my babies 😭💔