how do i tell my mom

hey, (ive never made a post before so bare with me please.) i am asexual. but not aromantic. i have been talking to aguy who is sooo sweet and so kind and kind off a nerd which i love. but its leading to kind of a relationshippy place. (he knows im ace, we have a buncb of mutual lgbt+ friends who are very open so he basically knew i was ace begore he knew who i was.) but the thing is ive been trying to stay away from relationships because i would need to tell my mom (im 17, did i mention that) that i am going on a date and stuff (i have a very protective mother and i love her to death) but this date conversation would evedently lead to a sex conversation... and heres the thing... i dont know how to tell my mom im ace. i feel like it will break her heart that she will never have bio kids... but i really like this boy so im coming to you guys.. how fo i approach the conversation of dating with my mom, and how do i come out?