How can I cope with so many of my friends becoming pregnant when I will never be able to?

When I was sixteen I was diagnosed with AML, and the bone marrow transplant I had put me into early menopause and made me infertile. At the time, the infertility was not on the top of my mind - surviving was. I am now a twenty six year old tenth grade English teacher, engaged, and many of my friends are now becoming pregnant, or have had children. My heart breaks over the fact that I cannot have an actual child of my own. My fiancee and I have discussed that we will apply for adoption, but I know that it is an extremely tedious process and I wish for a baby now. Sometimes when I'm alone I just cry.