My husband doesn't understand

✩M
I'm sorry if this is a bit long...
My husband and I very much want to have children at some point. He absolutely loves kids and would be an amazing dad. But I have pcos and hypothyroidism and he doesn't seem to understand that it's going to take me YEARS to conceive. My doctor has told me that I will be a very high risk pregnancy (85% likely to miscarry and will be put on bed rest practically the entire time) in the unlikely event I even get pregnant at all. He doesn't even want to start trying for two more years! He seems to be under the impression that I'm going to magically get pregnant on the first go. 
Neither of us are ready to have a baby right this second, but I'm scared that if we don't start trying soon, we'll end up not even having any kids. I don't want to have a baby when I'm pushing 40 (not that there's anything wrong with that, but I'm already high risk as it is and I don't want to push my luck by adding age as a factor.) My doctor has expressed that between my hypothyroidism and pcos, I may not be able to conceive naturally at all. So that might also be something time and money consuming we will possibly have to deal with. 
I have tried to explain how poor my fertility is to him multiple times and that if he wants to be a dad in a few years, we need to start trying now. What should I do to help him understand how serious the situation is? How can I convince him that we should start trying sooner rather than later?