From if to when to if

Before Tim and I got married and even a little after, we weren't entirely sure that we wanted to have kids. We both like children and we were emotionally and financially stable enough that getting pregnant would be a blessing, but we didn't know how we would handle it. With Tim flying all of the time and me spending my time split between research and my residency, we weren't sure how we would make it work. So, when our conversations turned to having children, we always said if.
As time went on, we both began to feel a strong urge to add a baby to our family and once we decided that it was what we wanted, we changed our if to when. When we have a baby we will... I think that phrase was uttered 500 times in the first 6 months of TTC. We talked about names, we talked about discipline, we talked about traveling and family and all of the things that change when you have a baby, which is pretty much everything.
After we reached the 1 year mark, and I had to officially accept that we were dealing with infertility (IF), I changed my phrases back to if. If we have a baby... If we get pregnant... I can't seem to make myself switch back. The uncertainty that we had at the start of our marriage about having children is back and I hate it. IF has made me if the possibility of children.
One of my good friends noticed this recently and said Could you try saying when? and I just looked at her and said No, I can't. She told me that every time I say if, she is going to insert a mental when because she has faith that it will happen for us somehow, someday. I really hope that she is right. I want my when back.