How soon can you tell?

Dina
I'm new to this whole ttc party. When I was younger and married I easily got pregnant. Since I have gotten divorced , raised my daughter and recently have found love again after many years alone. 
Last year we got pregnant but our angels received her wings before we got to meet her. Now after several months and many tears I find myself wishing for baby dust in my life. 
I just had AF at the beginning of the month and the last couple days I have been feeling different. Today, nausea got added to the list. So how do you know when to test. Because I don't want to push my emotions into thinking, and becoming disappointed.