new job at 21 weeks

Sara • I'm 32 a proud mother of a 5 year old son and I'm expecting baby number 2 in July.
Hey ladies and gents! 
I'm starting a new job on the 16th. I'm nervous and extremely thankful for the position. My days of living pay check to paycheck are over. However, when do I tell my employer I'm expecting? I don't want to hide my pregnancy but, I don't want to flaunt it either. Any input is greatly appreciated!!!