Uncontrollable sadness

I literally started crying at my desk this morning at work because my best friend told me yesterday she is pregnant with her third child, by accident. I acted happy for her, but secretly I feel sad because my husband and I  have been trying for almost 2 years with no success at all and also because I simultaneously feel like a bad person for feeling sad by her happy news. I feel totally hopeless and I'm so fearful my day will never come. I hate feeling like such a negative black cloud because I'm always so consumed by this!!