I Feel Like a Jerk 😔😔

My coworker announced back in May that she was expecting. Poor girl had a miscarriage in February that I didn't know about so this new baby is a big deal! For Father's Day, she went and got a 3D ultrasound to reveal the sex to her husband that morning when he came in from work. They watched the video together for his first time and rejoiced over their new baby boy :)
I'm so happy for her, and for the new life and excitement she and her husband are enjoying together. But I'd be lying if I said I didn't feel like crap. 
My dept (there are only 6 of us) keeps telling me "You can't get pregnant, because the mgr wouldn't know what to do if both of you were out of work!!" They don't know I'm trying. They don't know we've been trying for months and all I want in my entire being is to feel that little baby growing inside of me. 
How do I keep a smile on my face each time they insinuate that I must be happy for her and put my life on hold? How do I get excited about her new baby boy when that's what I pray for every day?