Why

Why is it that when someone tells me about their good new do I want to just break down and cry. I hate how consumed with envy I have because since June. In fact I remember one time being told how a customer at my last job had a miscarriage and I was SO jealous because she actually got to be pregnant for just a moment. I feel like such a horrible person because I felt this way. I know it is stupid but I still can't stop the feelings.