In a relationship with someone who has 2 kids

I just don't know what other way to find answers or talk to anybody without feeling judged or embarrassed... I have been with my boyfriend for about 8 months now. He has a 9 yr old and a 1 year old. We have been living with each other for about 6-7 months and everything has been fine for the most part.. he is 28, I am 19, sounds crazy huh ? Haha... we have recently went through a horrifying miscarriage on thanksgiving and still find ourselves tearing up every night asking why ... and how we would of had our baby this June... .. I love his kids and fortunately very close with both of them .. but my heart hurts .. even when it is a good day .. I feel like I just want to cry, i feel that I am no one .. I almost hate myself the way I feel because I always tell myself why couldn't I just have my own family .. I wish his two kids were actually ours and it just makes me sick when I think how young his son is ... I don't know what to do .. people ask if I have kids and I mention his 9 yr old but I can't seem to say that I also have a 1 yr old stepson.. I feel ashamed and I don't know why ..