Why can't it be me?

I just learned through Facebook this morning that my sister-in-law and her husband are expecting their first. And I just want to break down into tears. She has been through a lot of health issues, and was very sick for a while. She and her husband have no jobs. They still live with her grandparents. My husband's cousin and his fiance are due in about a month. My younger sister-in-law has a 2 year old son. People I used to work with a pregnant with their first, and their 4th. Friends of friends are pregnant. I've gone so far as to delete people from Facebook because I just can't stand to watch their pregnancies progress. I have been off birth control for 3 years, with no preventative measures since. We have been charting for the last year. We think we had a chemical in December, but no luck since. I just don't think I can pretend to be happy for everyone around me that is almost due, or just announcing. Everyone is telling my SIL congrats and that they are so happy for her, and I just can't...I feel myself turning bitter and hateful, but I don't know how else to feel.