Negative pregnancy test TTC

Janna • Married-Mother 1 boy and a girl is soon to join in July 2018.

Okay so I keep track of my periods and I was supposed to start Sunday. It is now Tuesday and still no sign of my period. But I have taken 3 pregnancy test and they are negative. I should also add I'm never late. I'm either always on time or start the day before my period is supposed to start. So now what? Is it possible that I am pregnant because we have been trying for like 3 months now.