Why does being childless make me feel this emptyness?

me and my husband have been trying to get pregnant for a couple years now, and have had many attempts and one loss. after every try when I start my period I break down into tears and become very depressed after knowing another attempt was failed. we have held off for along time tell we got much older (we met in the beginning of our high school years) I feel like there is something missing though and its a constant feeling that no matter how much he is there for me I still feel somethings not right (our relationship is wonderful so I know its not something between us), as well making things worse, we live on a air force base and I see I see all these people with their kids or pregnant. as well watching over 75% of my friends while we were growing up having kids between the ages of 16-19 a lot of them are now on there 2nd and 3rd child. I’ll walk past a baby store or clothes racks and I have to go and look around, it makes him sad to watch this. I’m so used to taking care of and baby sitting so many other baby’s that im ready to take care of my own. I think of somethings so special being created that’s from the two of us and it makes me hurt more. I was want us to have a baby to hold, love, feed, change it’s diapers, it just all sounds so perfect and life completing to me. I just dont understand why I feel so empty.