I can't take it anymore....

I cannot take it anymore. I am so depressed that I am seriously unhappy all the time. My husband and I have been trying for over 2 years, and I am at my limit. I found out tonight that one of my best friends is pregnant. I was so shocked and upset. I want to be happy for her, but it seriously broke my heart. I just don't know how to deal with this emotion. I just feel so alone....