Hello, my period is late and the test shows one line. My last period was…

Hello, my period is late and the test shows one line. My last period was on 04.04. My periods usually last 3–5 days, normally 5 days. Now I don’t know what to think. I haven’t been stressed and I don’t take any pills. I’m 36 years old, I have a 9-year-old daughter and a 5.5-year-old son, and I want a third ?