much needed rant

I have been ttc #1 for three years now. I've been told that it's unexplained infertility that everything is physically fine with me and dh. So why can't I get pregnant! I feel like I'm not being a good wife bc I can't give my husband another child (he has a child from a previous relationship that's my SD) Everyone is around pregnant and it kills me to know that I can't get pregnant and no one can give me answers as to why either... plus! My husband doesn't get why it is so upsetting... rant over...