I feel bad/jealous when

Leslie • I am a mother to a wonderful baby boy!
Someone asks my boyfriend about his 13 year old daughter he has with his ex girlfriend. The little girl is sweet, but his ex gf comes to his parents on holidays and tries to be my friend but takes small jabs at me. I feel sad when someone mentions how my be will get to give his daughter away when she gets married, and things like that I want a child of my own! Am I a bad person for feeling that way? We fight a lot about his ex gf and the whole situation and we shouldn't but I want a baby, but I have health issues and sometimes he will throw it in my face and say "at least she could have a child" :(