Sister In Law Pregnant

My husband and I have been TTC for about 6 months and I found out I had PCOS. Turns out my sister in law also has PCOS and they've been trying for about 8 months. They just announced she's pregnant this week. I'm super excited to be an aunt but I still feel the sting of jealousy and I am sad for myself. I feel selfish and I've been told by a coworker that I need to put off TTC so they can have their "moment". My husband and I don't want to wait any longer than we already have to. I know some siblings are pregnant at the same time and everyone is happy. I just don't want to make anyone mad. Thoughts/encouragement?