Fertility

So I was talking with one of my guy friends who I'm into and I pulled out my phone and started looking at my app and my period and such looking at my fertility window. And told him that we couldn't do anything cause I was in my window of fertility. And he looked at me super confused that I know and keep track of that. Is that weird? Am I wrong for keeping track? I'm on birth control. Why aren't guys taught more about this?