I felt the same way when my boss (the same age as me) announced her pregnancy. Now I came to learn later that this was a hard fought for pregnancy and she had had a miscarriage about a year earlier -- but I still felt jealous.
I don't know the solution but I have to admit with time it got less painful. I am still a bit wistful about it but I must admit I'm looking forward to working with her after she gets back from her maternity leave without having her lovely big belly staring me in the face.
I do hope you can figure out a way to feel a little better about it.
ttc #3 (#1 for DH)