Having a hard time....

So, I recently found out I was pregnant, like yesterday and I also have a 3 year old daughter. So lately, I get super emotional for having to discipline her. Like she's just like to play with things. For example, she was in the bathroom just spraying air freshener for no reason. I understand she is just a child, but I try to teach her doing certain things are wrong. I'm also trying not to fuss much since I'm pregnant. I just want to know how to handle her. Like I try to sit her down and talk with her and it seems to work until she finds something else to get into. Does anyone else have kids her age and how do you handle them?