Jealous of pregnant co-worker, what do i do?

So, I'm 24, married and desperately want kids. I've been married for almost three years, it'll be officially three on the 28th. The day we started dating we had my IUD removed and have been trying on and off ever since but never any luck. I'm friends with a coworker who just got married to a guy who has cheated on her five times. We've talked about how desperate I am for kids and how I worry that I'm never going to have them and how devastated that fear makes me, I just want it to be my turn. Today out of the blue she sends me a positive pregnancy test and tells me she's pregnant. On one hand, I'm happy she's happy and all I've said to her is congrats. On the other hand, I cried and all I can think is why can't that be me? My husband and I both would absolutely love kids and it seems like everyone but me can get there. I'm surrounded by pregnant women at work and it's almost all anyone talks about, im going crazy!