I'm 18 weeks and haven't told my job yet.

I just got a new job, well technically it's not new.. I used to work there last season but I switched stores and I just started and I'm 18 weeks pregnant and haven't told them yet. I haven't really started to show yet, I'm just worried to tell them bc they might treat me differently bc I'm 19 and no one really knows me yet. A lot of my family and friends have told me to wait to tell them, I just don't want to wait too long.. I don't know what to do!