Boyfriend and wanting a baby

Hi I'm 18 soon and I would like a child yes I know it is early but early menopause is genetic in my family my mam had it at 19 and I don't want to miss my chance at having a child of my own to love and to care for and to give it the best life I can... Me and my so have talked about when we are going to have a child and its his decision not mine he said 23 and then 20 but I might miss my chance not be able to have a child I told him that after I am 18 I would like to start trying but he has just brushed it off as like a I wasn't being serious... Does he even want a child!! ??